Resumen La ecografía Doppler es una modalidad diagnóstica que depende de un operador indispensable por disponibilidad, eficacia, coste y no invasividad. Además de conocimientos anatómicos y clínicos, exige un mínimo conocimiento de sus principios físicos y tecnológicos. Este artículo intenta repasar y esquematizar cómo ajustar las principales aplicaciones del equipo en la exploración Doppler mediante los botones y los controles (knobology). Complementa a la primera parte ya editada, en la que se explicaban los ajustes en la exploración en modo B. Realizar una exploración con una postura adecuada, que evite lesiones en el explorador (ergonomía), permite también aumentar nuestro rendimiento laboral. Conocer, entrenar y ajustar las funciones del eco Doppler de forma ordenada teniendo en cuenta al paciente y el estudio indicado hará que nuestras exploraciones sean más sencillas, rápidas, seguras y precisas.

Abstract Doppler ultrasound is an operator-dependent diagnostic modality, essential due to availability, efficacy, costs and non-invasive test. In addition to anatomical and clinical knowledge, it requires a minimum knowledge of its physical and technological principles. This article attempts to review and outline how to adjust the main applications of the equipment in Doppler scanning, using the buttons and controls (knobology). It complements the first part already edited, where the adjustments in the exploration in B mode were explained. Carrying out an examination with a suitable posture, which avoids injuries to the explorer (ergonomics), also allows us to increase our work performance. Knowing, training and adjusting the echo Doppler functions in an orderly manner, considering the patient and the indicated study, will make our examinations easier, faster, safer and more precise.

Abstract This article presents the development of a learning object to support teaching space geometry in basic education. The DICREVOA 2.0 and Waterfall methodologies were used for software development because both contain five similar stages that can be addressed simultaneously. The results present a web application with different geometric bodies and their main characteristics, capable of being projected in augmented reality on mobile devices directly from the browser without installing additional software. It is concluded that creating educational resources that incorporate virtual or augmented reality in web pages is possible using the World Wide Web Consortium proposal for using mixed reality, WebXR Device API.

Resumen Este artículo presenta el desarrollo de un objeto de aprendizaje para apoyar la enseñanza del tema de geometría del espacio en educación básica. Se utilizaron las metodologías Dicrevoa 2.0 y Cascada para el desarrollo de software debido a que ambas contienen cinco etapas similares entre sí que pueden abordarse de manera simultánea. Los resultados presentan una aplicación web con distintos cuerpos geométricos y sus características principales, capaces de ser proyectadas en realidad aumentada en dispositivos móviles directamente desde el explorador sin la necesidad de instalar software adicional. Se concluye que es posible crear recursos educativos que incorporen realidad virtual o aumentada en páginas web usando la propuesta del World Wide Web Consortium para el uso de realidad mixta WebXR Device API.

Resumo Este artigo apresenta o desenvolvimento de um objeto de aprendizagem para apoio ao ensino do tema geometria espacial na educação básica. As metodologias Dicrevoa 2.0 e Cascade foram utilizadas para o desenvolvimento de software porque ambas contêm cinco etapas semelhantes que podem ser abordadas simultaneamente. Os resultados apresentam uma aplicação web com diferentes corpos geométricos e suas principais características, capaz de ser projetada em realidade aumentada em dispositivos móveis diretamente do navegador sem a necessidade de instalação de software adicional. Conclui-se que é possível criar recursos educacionais que incorporem realidade virtual ou aumentada em páginas web utilizando a proposta do World Wide Web Consortium para utilização da API WebXR Device de realidade mista.

Abstract: Anorectal melanoma is rare, with 0.4 to 1.6% of all melanomas and 0.5% of anorectal malignancies. Frequently confused with hemorrhoidal disease and polyps. A 53-year-old female with no previous history presented with a foreign body sensation in the anal region and rectorrhagia of two months’ evolution. On proctologic examination, an indurated mass was detected in the left lateral region, 4 cm from the anal margin, and an examining glove came out with hematic debris. Colonoscopy reports a 2 cm pedunculated, friable, pigmented lesion located laterally in the dentate line. He underwent a wide local transanal resection (WLTR). Pathology reports malignant melanoma, positive resection margins, and in contact with neoplastic cells. She is subsequently treated with Nivolumab and adjuvant radiotherapy. The surgical options are WLTR and abdominoperineal resection (APR). Traditionally APR was considered the best option for locoregional control of the disease. However, recent studies report no difference in survival compared to WLTR. Most patients are diagnosed late in the disease; therefore, curative surgery is impossible.

Resumen: El melanoma anorrectal es poco frecuente con una incidencia de 0.4 a 1.6% del total de los melanomas, y 0.5% de los tumores malignos anorrectales; es frecuentemente confundido con la enfermedad hemorroidal y pólipos. Femenino de 53 años sin antecedentes, acudió por presentar sensación de cuerpo extraño en región anal y rectorragia de dos meses de evolución. En la exploración proctológica se detectó masa indurada en región lateral izquierda a 4 cm de margen anal, el guante explorador salió con restos hemáticos. La colonoscopia reportó lesión de 2 cm pediculada, friable y pigmentada localizada lateralmente en la línea dentada. Se somete a una resección local amplia transanal (RLAT). Patología reportó melanoma maligno, márgenes de resección positivos, en contacto con células neoplásicas. Fue manejada posteriormente con tratamiento adyuvante. Las opciones quirúrgicas son la RLAT y la resección abdominoperineal (RAP); de forma tradicional la RAP era considerada la mejor opción para el control locorregional de la enfermedad; sin embargo, estudios recientes no reportan diferencia en la supervivencia si se compara con la RLAT. La mayoría de los pacientes son diagnosticados en un curso tardío de la enfermedad, por lo tanto la cirugía curativa no es posible.

Abstract Commentary on the partial translation of Journal of an Expedition from Pirara to the Upper Corentyne, by Robert H. Schomburgk. In this article we briefly address the main translation procedures in our second experience with the records of the Prussian explorer and his expeditions in the border region between the Cooperative Republic of Guyana and Brazil. Based on Torres (2021), considering the principles of Ecotranslation, we seek to highlight moments that deal with the relationship between man and the environment, such as extractivism, ranching, trade, and cultural traits in general. For this work, we selected an excerpt from his travel journal referring to the second half of August 1843. Corentyne H Schomburgk Brazil 2021, 2021 , (2021) Ecotranslation environment extractivism ranching trade general work 1843 202 (2021 184 20 (202 18 2 (20 1 (2 (

Resumo Comentário da tradução parcial de Journal of an Expedition from Pirara to the Upper Corentyne, de Robert H. Schomburgk. Neste artigo tratamos brevemente dos principais procedimentos tradutórios em nossa segunda experiência com os registros do explorador prussiano e de suas expedições na região fronteiriça entre República Cooperativa da Guiana e Brasil. Com base em Torres (2021), considerando os princípios da Ecotradução, buscamos destacar momentos que tratam da relação entre homem e meio-ambiente, tais como extrativismo, pecuária, comércio e traços culturais de forma geral. Para este trabalho, selecionamos um trecho de seu diário de viagem referente à segunda quinzena do mês de agosto de 1843. Corentyne H Schomburgk Brasil 2021, 2021 , (2021) Ecotradução meioambiente, meioambiente meio ambiente, ambiente meio-ambiente extrativismo pecuária geral trabalho 1843 202 (2021 184 20 (202 18 2 (20 1 (2 (

Resumen Introducción Los estudios que se han llevado a cabo en torno al film de Alberto De Agostini siempre han sido abordados desde su visualidad y aporte histórico. Sin embargo, se vuelve urgente realizar una reflexión sobre los modos de evangelización y exterminio de los pueblos indígenas en el momento de la colonización del territorio austral y cómo éstos son completamente omitidos en las imágenes que registra el film. Tierras Magallánicas se centra en una construcción de imaginarios que ha dejado marcas en nuestra memoria reciente y en el mismo ser humano. Objetivo Este artículo pretende reflexionar el tema de la deshumanización en el proceso de colonización-evangelización de la Patagonia chilena por medio del análisis discursivo de las imágenes del film Tierras Magallánicas de Alberto De Agostini para determinar sus alcances en la sociedad actual al perpetuar una memoria colonizada. Método La metodología es cualitativa del tipo interpretativo, con un enfoque interdisciplinar, pues se estudian las imágenes del film Tierras Magallánicas de Alberto De Agostini desde las cualidades discursivas del mismo para determinar sus alcances en la sociedad actual, utilizando herramientas y fuentes provenientes de la teoría decolonial, la filosofía, la antropología y los estudios de la imagen, lo que permite abordar el objeto de estudio desde una óptica holística. Resultado El análisis discursivo de las imágenes del film evidencia una deshumanización en el proceso de colonización-evangelización de la Patagonia chilena, impactando en el sujeto ‘colonizador’, que se vio disminuido por la ambición, y en el sujeto ‘colonizado’, que sufrió una destrucción física y cultural. A su vez, visibiliza que la memoria fue colonizada al mismo tiempo, pues se perpetuaron las imágenes de una representación manipulada por el colonizador. Conclusiones El impacto de esta colonización de la memoria de una parte crucial de la historia magallánica, se evidencia en la sociedad chilena contemporánea en forma de racismos soterrados hacia los pueblos originarios. Por ello, se hace un llamado urgente a cambiar de piel, es decir, a construir una nueva historiografía que resignifique la memoria partiendo por la aceptación del espacio-tiempo colonizado en el que todos los chilenos habitamos, para construir un presente y un futuro más digno para todos.

Abstract Introduction The studies that have been carried out around Alberto De Agostini's film have always been approached from their visuality and historical contribution. However, it becomes urgent to reflect on the ways of evangelization and extermination of indigenous peoples at the time of the colonization of the southern territory and how these are completely omitted in the images recorded in the film. Tierras Magellanic focuses on a construction of imaginaries that has left marks on our recent memory and on the human being himself. Objective This article aims to reflect on the issue of dehumanization in the process of colonization-evangelization of Chilean Patagonia by means of the discursive analysis of the images of Alberto De Agostini's film Tierras Magellanic to determine its scope in today's society by perpetuating a colonized memory. Method The methodology is qualitative of the interpretive type, with an interdisciplinary approach, since the images of the film Tierras Magellanic by Alberto De Agostini are studied from its discursive qualities to determine its scope in today's society, using tools and sources from decolonial theory, philosophy, anthropology and image studies, which allows approaching the object of study from a holistic perspective. Results The discursive analysis of the images from Alberto De Agostini's film Tierras Magellanic shows a dehumanization in the process of colonization-evangelization of Chilean Patagonia, impacting on the 'colonizing' subject, who was diminished by ambition, and on the subject ' colonized ', which suffered physical and cultural destruction. At the same time, it makes visible that memory was colonized at the same time, since the images of a representation manipulated by the colonizer were perpetuated. Conclusions The impact of this colonization of the memory of a crucial part of Magellan history is evidenced in contemporary Chilean society in the form of underground racism towards native peoples. For this reason, an urgent call is made to change skin, that is, to build a new historiography that redefines memory starting from the acceptance of the colonized space-time in which all Chileans inhabit, to build a more present and future worthy for all.

Abstract This article consists of comments on the translation of A description of British Guiana, by Robert Schomburgk, a Prussian explorer in the 19th century. In general, the report turns into a statistical and geographical description of British Guiana. In this first contact with the work, we proceeded with a partial translation, considering excerpts related to the inhabitants, religion, and public instruction of the colonies of Demerara and Essequibo. Despite its eminently descriptive nature, the document also registers several social criticisms of the European occupation model, especially regarding the extermination of the natives and slavery. Methodologically, we observe the principles of eco-translation (TORRES, 2021) seeking to value the cultural context, ethics in translation of historical texts and the impact of human actions in the environment. Guiana Schomburgk th century general work inhabitants religion Essequibo nature model slavery Methodologically ecotranslation eco TORRES, TORRES (TORRES 2021 context environment 202 20 2

Resumo O presente artigo consiste nos comentários da tradução de A description of British Guiana, de Robert Schomburgk, explorador prussiano do século XIX. De maneira geral, o relato se volta para uma descrição estatística e geográfica da Guiana Inglesa. Neste primeiro contato com a obra, procedemos uma tradução parcial, considerando trechos relacionados aos habitantes, religião e instrução pública das colônias de Demerara e Essequibo. Apesar do caráter eminentemente descritivo, o documento também registra várias críticas sociais ao modelo de ocupação europeu, sobretudo no que diz respeito ao extermínio dos nativos e à escravatura. Metodologicamente, observamos os princípios da ecotradução (TORRES, 2021), buscando valorizar o contexto cultural, a ética na tradução de textos históricos e o impacto da ação humana no meio ambiente. Schomburgk XIX geral Inglesa obra parcial habitantes Essequibo descritivo europeu escravatura Metodologicamente TORRES, TORRES (TORRES 2021, 2021 , 2021) cultural ambiente 202 20 2

Apresentamos um dispositivo desenvolvido por nós, chamado Stellector, composto por um apontador laser que é precisamente guiado por dois motores de passo com o objetivo de explorar e ensinar conceitos astronômicos tendo o céu noturno como pano de fundo. A parte eletrônica é composta por itens de baixo custo e a parte mecânica é confeccionada em impressora 3D. O software de controle é escrito em linguagem HTML/Javascript de modo a poder rodar em qualquer dispositivo de comunicação portátil, tais como smartphones e tablets. A comunicação com o hardware do Stellector é via padrão bluetooth. Essas características garantem a portabilidade e autonomia necessárias para atividades de ensino de astronomia a céu aberto. Neste trabalho, esboçamos a estrutura e modo de operação do Stellector. Também ilustramos algumas atividades envolvendo conceitos astronômicos básicos através da observação do céu noturno. Por fim, discutimos as limitações, a precisão e as futuras melhorias do dispositivo.

We present a device, created by us and named Stellector, composed by a laser pointer which is precisely guided by two step motors with the purpose to explore and teach astronomy concepts having the real night sky in the background. The electronic part is made of low cost items and the mechanical part is 3D printed. The controller software is written in HTML/Javascript language in order to run in any portable communication device, such as smartphones and tablets. Communication with the Stellector hardware is via Bluetooth standard. These characteristics ensure the necessary portability and autonomy for outdoor astronomy teaching activities. In this work, we sketch the Stellector design and its mode of operation. We also illustrate some teaching activities involving basic astronomy concepts through night sky observations. Finally, we discuss the device limitations, its accuracy and further improvements.

Resumo Uma grande estátua de pedra foi trazida da Amazônia para a França em 1848 pelo explorador Francis de Castelnau. A escultura representa um personagem, aparentemente humano, agachado com as mãos no peito. Agora exposta no Musée du Quai Branly – Jacques Chirac, esta peça gerou uma forte controvérsia desde quando foi tornada pública. Em meados do século XIX, vários intelectuais brasileiros criticaram fortemente a atitude arrogante do francês que havia ‘saqueado’ seu patrimônio. Na realidade, as razões deste conflito eram bem mais profundas, uma vez que afetavam a própria identidade da nação, então em formação. De qualquer forma, uma peça de teatro foi escrita para zombar o explorador. Isto deu origem a dúvidas sobre a autenticidade do objeto, que persistem até hoje. Por isso, os autores apresentam aqui um estudo do artefato para determinar sua origem cultural, analisando as referências existentes para compará-lo com outras peças da Amazônia. Assim, os autores conseguiram validar a identidade ameríndia da estátua, quase 170 anos após sua descoberta.

Abstract A large stone statue was brought from the Amazon to France in 1848 by the explorer Francis de Castelnau. It depicts a being, apparently human, squatting, with his hands on his chest. Now exhibited at the Musée du Quai Branly – Jacques Chirac, this piece created a strong controversy since it was made public. In the mid-19th century, several Brazilian intellectuals strongly criticized the arrogant attitude of the Frenchman who had ‘looted’ their heritage. In reality, the reasons for this conflict are much deeper since they affect the very identity of the nation, then in formation. In any case, even a play was written to mock the explorer. This gave rise to doubts about the authenticity of the object, which has persisted to this day. The authors therefore studied the artifact to determine its cultural origin, while analyzing existing references to compare it with other pieces from the Amazon. They were thus able to validate the statue’s Amerindian identity, nearly 170 years after its discovery.

Resumo Entre 1505 e 1508, Duarte Pacheco Pereira, explorador e militar português, escreveu o Esmeraldo de situ orbis, um livro de “cosmografia e marinharia”, um dos mais importantes roteiros de viagem de seu tempo, o qual, além de desenhar as fronteiras e rotas comerciais conhecidas na África e no oriente, empenhou-se por traçar, ainda, o esboço de uma crônica sobre as navegações. Este artigo analisa o livro de Pereira, propondo que o autor apresenta uma legitimação política das terras conquistadas, ao mesmo tempo em que rompe com a geografia sacra, tipicamente medieval, e com a geografia mercantilista, típica dos portulanos mediterrâneos, para compor o primeiro roteiro de viagem moderno, expondo o desenho do novo mundo conhecido pelas navegações que vinham mapeando novas terras na África e na Ásia desde o século anterior.

Abstract Between 1505 and 1508, Duarte Pacheco Pereira, a Portuguese soldier and explorer, wrote Esmeraldo de situ orbis, a book on “cosmography and seamanship,” one of the most important travel guides of its time. In addition to drawing up the known trade routes and borders in Africa and the East, Pereira also set out to chronicle the journeys undertaken. This article reviews Pereira’s book, proposing that the author offers political legitimation to the lands conquered while breaking with both the mediaeval religious maps and the traders’ maps of the Mediterranean Portolans to develop the first modern travel guides. He exposed the new world presented by the navigations that had been mapping new lands in Africa and Asia since the previous century.

Resumo O artigo analisa as narrativas de viagem ao interior de Mato Grosso e Goiás publicadas em 1935 e 1936 pelo explorador paulista Hermano Ribeiro da Silva, que obtiveram considerável sucesso editorial e impacto no meio letrado brasileiro. Concentramo-nos em suas ideias sobre a relação entre o ambiente do Brasil Central e o homem sertanejo, sobre as potencialidades de exploração econômica da região e sobre o papel do Estado na condução de iniciativas capazes de promover sua incorporação efetiva à nacionalidade. Buscamos também compreender a fundamentação de seu discurso em conceitos e esquemas científicos genéricos dotados de poder retórico e argumentativo.

Abstract The article analyzes the travel narratives to the hinterlands of the states of Mato Grosso and Goiás published in 1935 and 1936 by the São Paulo-based explorer Hermano Ribeiro da Silva, which proved a great publishing success and had a considerable impact on lettered society in Brazil. The analysis focuses on his ideas about the relationship between the environment in Central Brazil and the man who inhabited it, the potential economic exploitation of the region, and the role of the State in orchestrating initiatives capable of promoting its effective incorporation into the nationhood. It also seeks to understand how he grounded his discourse on generic scientific concepts and schemas endowed with rhetorical and argumentative power.

Abstract In December 1880, The Chamber of Deputies forbade the export of hundreds of archaeological objects to the French explorer Désiré Char-nay. In this text the interpretations that have been given with regard to this process are questioned and an explanation is presented retrieving the ideas of Mexican elites concerning Mexican antiquities, the ways in which these goods were obtained, their ownership, which reveals why those objects were finally allowed to leave the country. Also, Charnay's actions to obtain archaeological objects are analyzed, as an example of how the elites had different standards to measure the importance of the explorations, depending on who performed them and who participated. These issues are examined with the aim to reinforce a different way of using and preserving cultural heritage.

Resumen En diciembre de 1880, la Cámara de Diputados negó la exportación de cientos de objetos arqueológicos al explorador francés Désiré Charnay. En este texto se cuestionan las interpretaciones dadas respecto a este proceso y se plantea una explicación que recupera las ideas de las elites mexicanas en relación con las antigüedades nacionales, lo que revela por qué se permitió finalmente que esos objetos salieran del país. Asimismo, se analiza el proceder de Charnay para la obtención de objetos arqueológicos, como una muestra de la forma en que las elites usaban distintos raseros para medir la importancia de las exploraciones, dependiendo de quiénes las realizaban y quiénes participaban. Se analizan estos temas con el propósito de reforzar una forma distinta de usar y preservar el patrimonio cultural.

Abstract: This article analyzes the image of the explorer Désiré Charnay, in other words, the idea and representation people have of this explorer, due to the story he wrote, which has been read without analyzing the contradictions that exist in his statements. This study will discuss the originality of his photographic work in two respects: on the one hand, analyzing it in contrast to the work of the Hungarian Pál Rosti, and on the other, discussing the scientific contributions of Charnay’s photographs, without neglecting to question the alleged activity of this “solitary explorer”. Thus, the hypothesis developed is that, like every image, the idea we have of this character is a result of the light emitted at a particular time and for a specific purpose. By changing the distribution of light, it is possible to recover other characters and intentions and new interpretations through more critical, contextualized explanations.

Resumen: Este artículo analiza la imagen del explorador Désiré Charnay, es decir, la idea y representación que se tiene sobre dicho explorador, producto del relato escrito por él mismo, el cual ha sido retomado sin analizar las contradicciones que existen en sus aseveraciones. En este estudio se discutirá la originalidad de su obra fotográfica en dos sentidos; por un lado, analizándola en contraposición con la obra del húngaro Pál Rosti y, por el otro, discutiendo los aportes científicos de las fotografías de Charnay, sin dejar de lado el cuestionamiento sobre la supuesta actividad de este “explorador solitario”. Así, la hipótesis que se desarrolla es que, como toda imagen, la idea que tenemos de este personaje es producto de la luz emitida en un tiempo y con un propósito específico; al cambiar la distribución de la luz, es posible rescatar a otros personajes, otras intenciones y nuevas interpretaciones a través de explicaciones más críticas y contextualizadas.

Resumen: Este artículo explora las relaciones creadas entre las obras de la exposición «No saber perquè però sabent per què» en el Centro de Arte Espronceda de Barcelona que realizó Pep Montoya (Barcelona, 1952) en enero de 2018. El artista, a pesar de ser un caso particular por su trayectoria, forma parte de una generación de artistas que en el contexto catalán se preocuparon por las estructuras básicas de la pintura. En su caso esta preocupación permanece presente, a pesar de haber abierto nuevas vías de exploración. Montoya ha sido un explorador de las zonas limítrofes de la pintura, incluso aquellas que tienen que ver con la representación.

Abstract: This article explores the relationships created between the works of the exhibition «No saber perquè però sabent per què» at the Espronceda Art Center in Barcelona by Pep Montoya (Barcelona, 1952) in January 2018. The artist, despite being a particular case because of his career, belongs to a generation of artists in the Catalan context who were concerned with the basic structures of painting. In his case, this concern remains present, despite having opened new ways of exploration. Montoya has been an explorer of the border areas of painting, even those that have to do with representation.

Resumen Este articulo presenta a la comunidad académica internacional los resultados de varios años de investigación sobre el fenómeno del rayo, dentro del grupo de investigación PAAS-UN de la Universidad Nacional de Colombia, específicamente sobre el llamado rayo del Catatumbo. Este fenómeno meteorológico se presenta desde la zona sur del lago de Maracaibo en Venezuela hasta la cuenca inferior del rio Catatumbo y más allá, en Colombia, de donde procede su nombre. El fenómeno tiene un interés histórico por saber cómo el explorador prusiano Alexander von Humboldt supo de su actividad en sus exploraciones a finales del siglo XVIII y un interés científico porque hoy en día se sabe que la región del Catatumbo presenta la mayor actividad de rayos del mundo.

Abstract This article presents to the international academic community the results of several years of research on the phenomenon of lightning, within the PAAS-UN research group of the National University of Colombia, specifically the so-called Catatumbo's lightning. This meteorological phenomenon occurs from the southern area of Lake Maracaibo in Venezuela to the lower basin of the Catatumbo River and beyond, in Colombia, where its name comes from. The meteorological phenomenon has a historical interest associated to Prussian traveler Alexander von Humboldt who learned of his activity during his explorations at the end of the 18th century, and a scientific interest, as it the Catatumbo region is considered to have the highest lightning activity in the world.

ABSTRACT The aim of this research was to determine the morphology and polarity of the QRS complex of the electrocardiogram in Holstein cattle, at different points of the body surface, as a reference for the diagnosis of cardiac alterations. Electrocardiograms were carried out in 20 derivations, nine bipolar and 11 monopolar. In total, 1800 records were observed from 100 clinically healthy animals and belonging to different age groups of both sexes. The QRS complex was coded according to its morphology. Twenty two different forms were detected, with greater appearance frequency of the R wave as the only component of the complex in all derivations. The greatest diversity in the polarity of the QRS complex and in morphology was presented in the standard bipolar derivations of extremities. On the contrary, the maximum number of the forms of the QRS complex in the shoulder and base-apex bipolar derivation was very low, as in the monopolar derivations V1H, V3H, V10 and V4. It is concluded that in the derivations in which the electrodes measure potential differences between the base-apex regions of the heart, or in which the scanning electrode is placed in one of these two areas, the polarity of the QRS complex waves is very stable and the morphology varies very little. This makes them an important reference to detect alterations of the electrical conduction system of the heart t in cattle.

RESUMEN El objetivo de esta investigación fue determinar la morfología y la polaridad del complejo QRS del electrocardiograma del bovino de la raza Holstein, en diferentes puntos de la superficie corporal, como referencia para el diagnóstico de alteraciones cardíacas. Los electrocardiogramas se efectuaron en 20 derivaciones, nueve bipolares y 11 monopolares; en total se observaron 1800 registros procedentes de 100 animales clínicamente sanos y pertenecientes a diferentes grupos etarios de uno y de otro sexo. El complejo QRS fue codificado de acuerdo a su morfología y se detectaron 22 formas diferentes, con mayor frecuencia de aparición de la onda R como único componente del complejo en todas las derivaciones. En las derivaciones bipolares estándares de extremidades se presentó la mayor diversidad en la polaridad del complejo QRS y en la morfología. Por el contrario, el número máximo de formas del complejo QRS en las bipolares de hombro y de base-ápice fue muy bajo, al igual que en las derivaciones monopolares V1H, V3H, V10 y V4. Se concluye que en las derivaciones en las que los electrodos miden diferencias de potenciales entre las regiones de la base y del ápice del corazón, o en las que el electrodo explorador se coloca en alguna de estas dos áreas, la polaridad de las ondas del complejo QRS es muy estable y la morfología varía muy poco, lo que las convierte en una referencia importante para detectar alteraciones del sistema de conducción del impulso eléctrico en el corazón del bovino.