46 



Messrs. Dreyer, Ray, and Walker. [Sept. 30, 



aortic percentage is 0-609. The variations of the aortic constant show no 

 periodicity, but the aortic percentage decreases very greatly (although not 

 regularly) as the animals increase in weight. When the aortic area {i.e. area 

 of the cross-section of the aorta) is calculated by our formula, the average 

 deviation of the observed from the calculated figures is 16 - 49 per cent., while 

 it is 26'34 per cent, if the area be calculated in per cent, of body weight. 

 If the value -l 72 be taken for n, k becomes 24-15. 



Table VI. — Babbits (grouped). 



Group. 



Numbers of individuals 

 from Table V in 

 group. 



Average body weiglit. 



Average radius of aorta. 



Average area of aortic 

 cross-section. 



i 

 ii 



-Si 



Aortic cross-section as 

 percentage of body 

 weight. 



a> 

 a 



"3 r, t 1 



Cj ■ 



'1 I" " 



?^ 

 m ^ 

 m 

 p 



O 



Difference between 

 cross-section calcu- 

 lated and observed. 



Cross-section calculated 

 as percentage (0 "628) 

 of body weight. 



Difference between 

 cross-section calcu- 

 lated and observed. 







grm. 



mm. 



sq. mm. 









per cent. 





per cent. 



A 



1-2 



340 



0-961 



2 91 



21 6 



856 



2-84 



2-46 



2-14 



35 -98 



B 



3-4 



649 



1 -29 



5 -27 



18 -7 



0-812 



4-45 



18 -43 



4-08 



29 17 



C 



5-6 



1375 



1 -44 



6-51 



26 -0 



0-473 



7 65 



14 -9 



8-64 



24 -65 



D 



7-8 



1763 



1 72 



9 1 



22 -2 



0-516 



9 13 



-33 



11 -07 



17-71 



E 



9-12 



2207 



1 -84 



10-69 



22-1 



-484 



10 -71 



0-19 



13 -86 



22 -87 



Average 



22 -1 



0-628 





7 26 





26 -08 



In Table VI the rabbits are arranged in five groups according to weight, 

 and the aortic constant and aortic percentage are calculated from the average 

 figures of these groups. In this ease the best n is 071, giving an average 

 k of 22*1. The variations in the aortic constant are without periodicity, but 

 the aortic percentage falls gradually, though not quite regularly, from - 856 

 in the lightest, to - 484 in the heaviest group. Using the above values for n 

 and k, the average deviation of the observed figures from the calculated is 

 7'26 per cent., while it is 26 - 08 per cent, (between three and four times as 

 great) if the area be calculated as a percentage of body weight. 



We now return to examine the question of sex as regards its bearing on the 

 size of the aorta in these mammals. Since the number of our observations 

 within any one of the species can hardly be regarded as sufficient to justify a 

 general inference, we have taken all three species of animals together and 

 made the figures comparable, inter se, by reducing them in terms of a common 

 standard. When this is done, and the male and female animals are taken 

 separately, it appears that the sectional area of the aorta in the male expressed 

 as a function of the body surface is about 3 per cent, greater than it is in a 



