STRUCTURAL CHARACTERS OF ANIMAL ORGANISMS. 29 



FIG. 4. 



they have been called intercellular substance, while in others they 

 appear as materials specially modified for the furtherance of the 

 functions of the special tissues. 



IV. Cell Contents. Regarding protoplasm as the essential 

 living part of the eel), 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 

 animal textures, particularly that 

 called Connective Tissue, we com- 

 monly find large quantities of fat 

 formed and accumulated to such a 

 degree in the cell that the proto- 

 plasm can be no longer recognized 

 as such. Its remnant is devoted 

 to forming a limiting 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 secre- 

 tion 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- 



Cell from connective tissue con- 

 taining large fat globule (a), and 

 showing protoplasm (p), and nu- 

 cleus (n), (m) membrane. (Ran- 

 vier.) 



