2 FIRST LESSONS IN ZOOLOGY. 



The Difference between Mineral and Living Bodies. Now 

 how do living bodies differ from minerals? The earth and 



sea teem with plants and animals each 

 after their kind, and yet all these 

 myriad forms are alike and differ from 

 minerals in one respect: their bodies 

 are composed of a substance like a clear 

 jelly or the "white" of an egg. This 

 jelly-like substance is called proto- 

 plasm, and it is contained in sacs of 

 microscopic size, called cells (Fig. 1). 

 Our bodies are made up of cells, and 

 so far as we know there is no living 

 being, whether plant or animal, which 

 is not formed of this all-important 

 living substance. Hence we are led 

 to believe that this living jelly is 

 the basis of life The lowest one- 

 c S eii v S leS (Magnifi l ed550 celled plants and animals are com- 

 times - ) posed of nothing but this fundamen- 



tal jelly-like matter; and the seeds and eggs of the higher 

 many-celled plants and animals are mostly made up of it. 



This living matter or protoplasm consists of mineral 

 matter, to be sure, but so combined as to form a substance 

 not found in the mineral world. 



The most important materials composing protoplasm are 

 gluten, a sticky substance made from flour and like mac- 

 aroni, and albumen, which can be made either from vegeta- 

 ble starch or from the white of an egg, by heating them in 

 water. In the protoplasm of plants are starch, cellulose, 

 and many other substances, while in that of animals are 

 gelatine, fibrin, etc. ; but fundamentally they are alike, for 

 when analyzed by the chemist they are both found to be 

 formed of proteids, which are complex compounds of the 

 elements carbon, hydrogen, oxygen/, nitrogen, sulphur (and 

 sometimes phosphorus), combined in very nearly the same 

 proportions. Moreover the simplest one- celled plants and 



