COMPARED WITH THOSE OF ANIMALS. 37 



globular or dodecahedral cells containing fat in their interior, 

 to wliicli the term adipose tissue is applied, in works on ana- 

 tomy and physiology. 



Fig. 5. 



Cells of adipose tissue. 



These cells may be seen at any time, even with micro- 

 scopes of a very inferior quality. They retain their original 

 cellular form, and hence the cellular character of adipose 

 tissue has been long known. 



The number of tissues in the animal is much greater 

 than in the plant. Their morphology from the same cellu- 

 lar type is still a matter which requires further elucidation. 

 Their differences, like those of plants, are not always well- 

 marked, one form of animal tissue passing into another by 

 insensible shades of gradation. In man and other animals 

 of a high grade of organization, the tissues are by far the 

 most numerous and well-defined. As we descend in the 

 chain of being, these distinctions between the tissues become 

 gradually effaced, the organs are not so numerous, and the 

 whole structure is greatly simplified. The soft body of a 

 snail, for example, is much more uniform in its composi- 

 tion than the body of a bird or a quadruped. The parts 

 of the osseous frame-work are gradually blended together, 

 the bones become cartilaginous, and finally disappear 

 4 



