56 



ANATOMY 



weight. The relation to body weight is not close, but the rela- 

 tion to the area of the body surface is good. 



Table 22 gives the results of these determinations for body 

 surface and shows that on the average and neglecting signs 

 the mean deviation amounts to 1.18 per cent, while if signs are 

 considered, it is but 0.27 per cent. 



The formula used for computing the area of the cross sec- 

 tion of the aorta is A = W- 72 k where A is the area of the aorta; 

 W- 72 the body surface based on W the weight of the body in 

 grams, and k a constant, peculiar to the rat and having the 

 mean value of 21.9. 



TABLE 22 



Cross section of the aorta on body area and body, weight 



Vascularity of central nervous system. Using one hooded rat 

 and nine Albinos, Craigie ('20) has determined the vascularity 

 of different parts of the nervous system. Four of these rats 

 were from The Wistar Institute and five from Toronto. Four 

 of the total number were females. All were mature. The ner- 

 vous system was injected with carmin gelatin and the total 

 length of the injected vessels in M determined in a unit volume 

 of tissue at 21 localities. There was no significant difference 

 between the results from the Institute rats and those from 

 Toronto. 



The females however show a slightly better vascular supply- 

 especially in the gray matter. 



The mean values for total lengths hi the entire series of rats 

 are given in detail according to localities in table 1 (Craigie, 



