Observations on the circulatory functions of 4 giraffes are recorded. Both the right and the left heart were catheterized under local anesthesia with a miniature manometer. Cardiac output was determined by employing both indicator dilution method and the Fick principle. Other parameters, such as the circulation time, blood volume, velocity, right and left ventricular pressure ascent as well as the changes in blood pressure occurring with changes in the Posture of the head were recorded. The difficulties of the experiments created certain limitations in their interpretation. The arterial blood pressure is high by human standards and adequate to maintain cerebral perfusion without other means of support. The arterial pressure pulse contour suggests a relatively lax vascular bed with considerable reserve distensibility. Values for cardiac output and blood volume were roughly comparable to those recorded in domestic cattle of the same approximate weight.

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Comparative mammalian physiology not only is important as an intellectual discipline in its own right, but it also provides a perspective which can contribute to the understanding of physiological processes in a given species.As an example, those functions of the organism which appear related to body weight or to body surface area can be studied over a wide range of animal size, providing more extensive data for the precise analysis of relationships than could be obtained from investigations confined to members of a single species. In recent years a strong increase in interest in physiological studies on large mammals has been evident.'-6 The discussion which follows is based on circulatory and respiratory observations obtained on four giraffe in South Africa a t an elevation of 2375 feet and on 26 domestic cows studied a t three centers in the United States a t 400 feet or less above sea level, as well as on data reported from other investigative groups. I n certain areas comparison of the findings in giraffe and cattle is made with those in man, dog, and other mammals. In the choice of material considerable selection has been exercised and preference given to findings providing new viewpoints for discussion or permitting direct comparison between species.The species of primary interest in this presentation-domestic cattle (cows) and giraffe-are large ruminants of approximately comparable body weight, namely, 650 to 1,450 pounds (295 to 659 kg.). Both of these animal groups belong to the same suborder (Pecora) but to different families, the Bovidae and Giraffidae, respectively. Although giraffe sometimes attain a height of 16 feet and are said to reach 20 feet rarely, the tallest animal in the present group was approximately 12 feet in height. FIGURE 1 shows this animal and a domestic cow of comparable weight in proper scale relationship. I t can be seen that although there is a striking difference in height (11'7.5" versus 4'6") the position of the heart is roughly halfway between hoof and head in both animals.

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