34 



PROTOPLASM AND TUE CELL. 



animal, being always associated with quantities of other sub- 

 stances. Even the white of an Qgg^ which is usually taken for 

 a typical proteid, contains only twelve per cent of actual proteid 

 matter, the remainder consisting cliielly of water. The follow- 

 ing table shows the j^ercentage of proteids and other matters in 

 a few familiar organisms and their products : 



PROXIMATE PERCENTAGE COMPOSITION OF SOME COMMON 



SUBSTANCES.* 



Arranged according to richness in Proteids. 



I 



1 

 2 



3 

 4 

 5 

 6 

 7 

 8 

 9 



10 

 11 

 12 

 13 

 14 

 15 

 16 

 17 

 18 

 19 

 20 

 21 

 22 

 23 

 24 

 25 

 26 

 27 



Apples.. 



Indian corn, aerial portion fresh 



Oysters, shells included 



Turnips 



Melons. .... 



Sweet potatoes 



Crayfish, whole 



Irish potatoes 



Clams, round, shells included... 



Oats, aerial part fresh 



Grass, " " " 



Peas, " " " 



Cow's milk. 



Flounder, whole. 



Lobster, "■ . 



Poplar and elm leaves, fresh. . . . 



Crab, whole 



Brook trout, whole 



Hen's eggs, shells included 



Mutton " chops " 



Chicken, whole 



Beef, heart 



Beef, liver.. 



Beefsteak, round, lean . 



Beans 



Cheese.. 



Cheese from skimmed milk 



All proteids have nearly the same chemical composition and 

 similar physical properties, however different may be the forms 

 of protoplasm in which they occur. The analysis of protoplasm, 

 or ratlier of the proteids which are its basis, teaches us really 

 nothing of its vital properties, but serves only to sliow the 

 chemical composition of the material basis by which these are 

 manifested. 



Proteids are so called from tlieir resemblance to protein 

 (Trpcyrob, first)^ a hypothetical substance first described and 



* Compiled chiefly from tables of food-composition prepared by W. O. Atwater 

 for the Smithsonian Institution, though a few examples have been added— viz.- 

 numbers 2, 10, 11, 12, 16— from Johnson's How Crops &row, N. Y., 1883. 



