39 



The Size of the Aorta in Warm- Blooded Animals and its 

 Relationship to the Body Weight and to the Surface Area 

 Expressed in a Formula. 



By Georges Dreyer, William Eay, and E. W. Ainley Walker. 



(Communicated by Francis Gotch, F.R.S. Eeceived September 30, — Read 

 December 5, 1912.) 



(From the Department of Pathology, University of Oxford.) 



In recent years it has become increasingly evident that many of the most 

 important problems of physiology and of experimental pathology cannot be 

 investigated in a satisfactory manner until accurate data have been made 

 available regarding the quantitative differences which are exhibited by the 

 organs, tissues, and fluids of the body in normal animals of different species 

 and of varying weights. Results obtained with animals of any given weight 

 cannot be applied, even within one and the same species, to yield con- 

 clusions regarding animals of a different weight until it has been determined 

 with precision how the various organs and tissues of the body are related 

 to the size of the individual. Moreover, it will not be possible to compare 

 one species with another, or to apply the results deduced from any given 

 species to any other species of animal, until we can establish the existence 

 of some kind of quantitative correlation between the measurements in 

 different species. That this will prove to be possible seems likely from an 

 examination of the results already obtained by us in studying the various 

 factors which influence the circulatory system and determine the size of 

 the heart (1). 



In connection with our study of the blood and cardio-vascular system 

 under normal and pathological conditions, it was shown that the blood 

 volume of normal animals of any given species is proportional to their body 

 surface, and follows the formula B = W n fk, where k is a constant for the 

 species and n is approximately - 70-0 - 72 (2), (3). Accordingly it became 

 of interest, in view of the theories which have been put forward regarding 

 the volume of the blood and the size of the aorta in chlorotic conditions, to 

 endeavour to determine how the size of the aorta is related to the weight 

 of the individual in any given species of animal. 



For this purpose we have made a series of measurements of the aorta in 

 various mammals and birds (4). In the case of the birds some of the 

 measurements which we have made use of were carried out by Mr. H. K. Fry 



