STRUCTURAL CHARACTERS OF ANIMAL ORGANISMS. 37 



FIG. 4. 



modified for the furtherance of the functions of the special 

 tissues. 



IV. Cell Contents. Regarding protoplasm as the essential 

 living part of the cell, under this heading will come only those 

 extraneous matters which are the outcome of protoplasmic ac- 

 tivity. 



The cell contents which are present with such constancy and 

 in such variety in vegetable cells, form in them an all-important 

 part ; but in most animal cells the contents do not occupy such 

 a striking position. 



No doubt animal protoplasm is quite as capable as that of vege- 

 tables of making out of its own substance, or the nutriment sup- 

 plied to it, a great variety of mate- 

 rials, but these are seldom stored in 

 such large quantities in animal cells 

 as in those of plants. 



In the cells of some kinds of ani- 

 mal textures, particularly that called 

 Connective Tissue, we commonly find 

 large quantities of fat formed and 

 accumulated to such a degree in the 

 cell that the protoplasm can be no 

 longer recognized as such. Its rem- 

 nant is devoted to forming a limit- 

 ing membrane for the fatty contents, 

 so that the cell is converted into an 

 oil vesicle, and here certainly what may be termed the contents 

 become the most important part of the cell. In various gland cells, 

 also, as will be seen hereafter, different substances are made and 

 stored up temporarily in the protoplasm, and these can be seen as 

 bright refracting granules, and are subsequently discharged in the 

 secretion of the gland. 



In other cells again (liver) nutrient material allied to starch 

 may be deposited in considerable quantity, just as starch is stored 

 in certain cells of a plant, but owing to the greater and more con- 

 stant activity of animals, the amount laid by never attains any- 

 thing like that found in the store textures of vegetables, where 



Cell from connective tissue con- 

 taining large fat globule (a), and 

 showing protoplasm (p), and nucleus 

 (n), (t) membrane. (Ranvier.) 



