232 



HITCHCOCK'S ANATOMY 



true of ruminants. The largest animals, such as the elephant, 

 have very small corpuscles. In some of the camels and llamas 

 the corpuscles are large and somewhat elongated. The same 



is true of the dromedary. 

 Crystalline substances 

 are found in the blood 

 of other mammals as 

 -well as man. The an- 

 nexed cut shows crystals 

 from the blood of the 

 Guinea pig. 



The distribution ot 

 the arteries of quadru- 

 peds is a subject of con- 

 siderable interest. In 

 grazing animals, which 

 hold their heads low, in 

 addition to large arterial trunks, we find a great number of 

 very small ones, which are exceedingly tortuous in their course, 

 called " Wonder Nets." This arrangement is to prevent a too 

 rapid flow of blood to the head by the force of gravity, which 

 would of necessity take place when the head is so constantly 

 in a dependent position. A similar disposition is seen in the 

 limbs of the sloth and other animals which are like them in 

 tardiness of movement. In the fore-leg of the lion, where 

 great muscular force is exerted, the main artery passes through 

 a perforation in the bone, so as to secure it from obstruction 

 to the flow of blood by pressure of the rigid muscles. 



413. Heart of Birds. — The heart of birds is highly mus- 

 cular and of very large size in proportion to the bulk of the 

 body, and in general structure resembles the same organ in 

 mammals. The valves of the right ventricles, however, are 

 supplied with a strong band of muscular fibers, which gives 



412. What is peculiar about the blood discs or corpuscles of the larger animals? 

 What is the form of nearly all of them ? In what animals ar e they oval ? What are 

 Wonder Nets, and why are they introduced ? 413. What is worthy of note with refer- 

 ence to the heart of birds ? 



FlG. 230. 



Blood Crystals of the Guinea Pig. 



