1912.] Tlie Size of the Aorta in Warm- Blooded A nimals. 43 

 Table II. — Guinea-pigs (grouped ). 



Group. 



Numbers of individuals 

 from Table I in group. 



Average body weight. 



Average radius of aorta. 



o 

 3 



° a 

 = i 



V 



be f 



1 ? 



i 

 ii 



'-f ._ 



oo 



i O 

 an -D 

 ? 



~ "= ^ 

 O g M 



'■f II 11 



- 



o 



5 k ■ 



- - — 



= = - 



CO 



R — 



.2 ° 

 .— — 



:- -; = 



— x ™ 



ill 

 FE ^ — 

 P 



— 



"= 2, 



_r 



£ tOM 



: : J 

 ■- - . 



— .- 



r — — 



- o ~ 



i ^ 

 r. 7. — 



? B o 



- — 



-° & 

 a 



o o 

 '— — 



- S = 



— "A ~ 

 1 J - 



o o| 

 P 







grm. 



mm. 



sq. mm. 









percent. 





per cent. 



A 



1-5 



156 



0-679 



1 -45 



26 -2 



0-93 



1 -48 



2-03 



1 -22 



18 -85 



B 



6-13 



218 



0-794 



1 -98 



24-4 



0-91 



1 -89 



4-76 



1 -7 



16 -47 



C 



14-20 



328 



0-904 



2-57 



25 2 



0-78 



2-55 



0-78 



2-57 



o-o 



D 



21-27 



478 



0-998 



313 



27 -1 



0-65 



3 32 



5 -72 



3-73 



16 -09 



E 



28-35 



726 



1 -204 



4 "55 



25 2 



0-63 



4-48 



1 -56 



5-66 



19 -61 





25 -6 



0-78 





2-97 





14 -2 



exhibits no periodic variation as the weight of the animal increases, the 

 figure representing the sectional area in percentage of body weight decreases 

 with absolute regularity from 0"93 to 0'63. 



As regards the question of sex. if the males and females be considered 

 separately in Table I, it will be seen that the average k for the IS males is 

 smaller than the k for the 17 females. Thus, with u equal to 0*71, the h for 

 the males is 23 - 9, and that for the females 26, while with n equal to - 72, Jc 

 is 25 - 4 for the males and 27"6 for the females, indicating in each case that 

 the male animals had somewhat larger aortas than had the females of 

 corresponding weights. But this is a point to which we shall return. 



In Table III are given the figures and calculations for the aortas of 

 27 rats, ranging in weight from 301 to 303 grm. (i.e. increasing more 

 than tenfold). The average aortic constant (I) is 2T37, with an n of 0*71, 

 which is the best n for these observations, and the average aortic percentage 

 (i.e. sectional area of aorta expressed as a percentage of body weight) is 1"27. 

 It is seen that, as in the case of the guinea-pigs, the variations of the aortic 

 constant show no periodicity, but the aortic percentage decreases markedly 

 and steadily, although not regularly, as the animals increase in weight. If 

 the area of the aortic cross-section is calculated by our formula, the average 

 deviation between the calculated and the observed figures is 11-09 per cent., 

 while it is 19 - 72 per cent., or nearly twice as large, when the area is 

 calculated in per cent, of body weight. If the value - 72 be taken for n, h 

 becomes 22 - 36, and, if these values be used in calculating the sectional 

 aortic area by our formula, the average percentage deviation of the observed 

 from the calculated figures is 1T37 per cent. 



