460 Mabel Bishop 



blood supply, not by compromise as in Teras XII where a median com- 

 pound vessel was sufficient to meet the emergency, but by providing 

 two separate and distinct head supplies. Therefore, the course of the 

 arteries from the origin of the four common carotids is almost identical 

 in the two heads, and furthermore, the distribution is in general as 

 normal as it would be in two separate lambs standing side by side [see 

 Plate VI]. The distribution of the head arteries is also very similar 

 to the condition in normal pig, the chief differences being changes char- 

 acteristic of ruminant and non-ruminant arteries. It does not seem 

 necessary, therefore, to describe in detail the course of these arteries, but 

 only to call attention to salient differences. The first chief difference 

 between pig and lamb, normal and cosmobiotie, is that in pig there is 

 no anterior aorta. The subclavians arise independently from the aortic 

 arch; the right subclavian gives rise to the common carotids by a 

 short innominate trunk, which is practically the same as the cephalic 

 trunlv of the lamb, only shorter. Chauveau® claims the absence of an 

 internal carotid artery in sheep, Avhich is compensated by a branch from 

 the occipital. Since the internal carotid frequently arises by a common 

 trunlv with the occipital, I am inclined to think that Chauveau's occipital 

 branch and the internal carotid are one and the same vessel. 



The difference in origin of the Unguals and facials can scarcely be 

 called a characteristic difference, for they arise by a common trunk from 

 the external carotid quite as frequently as by separate origins. Aside 

 from the rise of the great arteries from the heart, the differences between 

 corresponding arteries of pig and lamb that have been pointed out, and 

 others that have not, are of minor importance, since they apply only to 

 origin and not to distribution, and occur quite as frequently in normal 

 organisms as in monsters.^° Between heads A and B of Teras XV only 

 two differences are worthy of attention. The most striking is the absence 

 of one lingual in head A; the one present courses along the middle of 

 the tongue instead of to one side. This single artery to the tongue of 

 head A is the point I had in mind when I stated earlier in the paper that 

 there was a third reason for supposing that head A had not suckled 

 during the life of the cosmobion. If this tongue had functioned very 



"Cbanveaii, The Comparative Aiiat. of Domesticated Animals, p. 592. 



'"Chaiiveau. Ibid., p. 520. "In a pm-ely anatomical and physiological point 

 of view (however) these anomalies are of no moment, as it matters little 

 whether the blood comes from one source rather than another . . . pro- 

 vided its relations are not altered, and the principle of immutability of con- 

 nections is maintained." 



