'604 



COMPARATIVE PHYSIOLOGY. 



It is owing to differences in the shape and size of these cells 

 chiefly that the structural variations of connective tissue in dif- 

 ferent regions of the hody are due. 



Fig. 440. — Loose network of connective tissue from man, in which are connective-tis- 

 sue corpuscles among the fibers (Eollet). a, a, capillary with blood-cells. 



Elastic Tissue. — This form of tissue is also of very wide distri- 

 bution and of great importance in the economy of a comphcated 

 living organism that must constantly adapt itself to the stress 

 and strains of existence. In its purest form it occurs, e. g., in 

 the ligamentum nuclese of the ox, as a somewhat yellow, tough, 

 elastic structure easily flbrillated when boiled, but with diffi- 

 culty torn asunder when fresh. Under the microscope it ap- 

 pears as fibers with a very distinct outline and of varying size. 

 In the arteries, as already referred to, it forms a sort of elastic 

 membrane of the utmost importance in the functions of these 

 organs. 



Bone. — In a l9ng bone, as the femur, in the dried state, we 

 recognize a compact shaft and two extremities of a more porous- 

 nature, while the central portion of the former presents a more 

 or less circular cavity, the medullary canal. By treatment 

 with hydrochloric acid abundance of lime salts njjy be ob- 



