AND PHYSIOLOGY. 



231 



410. Aorta and Pulmonary Veins— The manner in which 

 the Aorta and its branches are given off varies greatly in these 

 animals, as may be seen by the cut. The number of Pulmo- 



Fig. 228. 



E 



a h 



mil 



* 3 2 3 2 3 2 3 23 2 3 7 z , ? 



a & a 6a b a b a b a b a b a 



Diagram of the Principal Varieties of the Aorta in its Principal Branches in a, Man ; 

 b, Elephant c, Cetacea ; d, Bat; e, Carnivora; r. Seal; g, Ruminants; ii, Reptiles. 

 1, Right Subclavian. 2, Right Carotid. 3, Left Carotid. 4, Left Subclavian. 5, Verte- 

 bral, a, Ascending and b Descending Aorta. 



nary Veins varies upon the different sides of the body, and 

 is generally according to the number of lobes in the lungs, 

 the relations of the sides being represented by the formula 

 3 + 2. 



411. Economy of Diving Animals —In diving animals the 

 vena cava is capable of great dilatation, in order to contain an 

 unusual quantity of blood which accumulates there when the 

 animal suspends respiration under water, since it can not be 

 purified except in the lungs. Still further protection to the 

 heart in diving animals is seen in the vena cava ascendens, 

 where a circular muscle, by its contraction, can completely cut 

 off the flow of blood to the heart Fig. 229. 



from the lower extremities. ^ 



412. Blood Corpuscles of f* a h®3 

 Mammals— Wonder Nets.— ^® 



The blood of mammals, for 

 the most part, presents small 

 round, disc-shaped corpuscles, 

 similar to, but smaller than those in man. This is especially 



* A 



Red Corpuscles of the Ox. A, In their 

 Natural State, a, Seen in Profile. b> Seen 

 on the Surface. B, Altered Corpuscles. 



410. What is peculiar about the aorta and pulmonary veins in many mammals? 411. 

 What is the arrangement of the vena in diving animals? 



