PROTOPLASM. 19 



been subjected to all forms of analyses. The chemist 

 tells us that protoplasm, whether animal or plant, 

 yields the following elements : carbon, hydrogen, oxy- 

 gen, nitrogen, and some sulphur. He is unable to 

 tell us the combining relation of these elements in 

 protoplasm, for the obvious reason that in his anal- 

 yses protoplasm as living substance is destroyed and 

 life has departed. But it is of interest to know that 

 these elements, combined in some mysterious and 

 unknown way, make this marvelous substance liv- 

 ing matter. It is also of interest to reflect briefly 

 upon the individual peculiarities of these elements. 

 Carbon is a solid, exists free in nature, and remark- 

 able for its allotropic forms, it being found as coal, 

 or graphite, or diamond. Its combining power with 

 other elements is extensive, and its durability is 

 well known. Hydrogen is a gas. It is the lightest 

 known substance. It is practically never found 

 free in nature. Its combinations with other ele- 

 ments are many, forming often very stable com- 

 pounds, the most common being its union with oxy- 

 gen to form water. Oxygen is a gas and found free 

 in nature, forming nearly 20 per cent, of the atmos- 

 phere. Its combining power is perhaps the most 

 extensive of all the elements, forming many stable 

 oxides. Nitrogen is also a gas and found free in 

 nature, forming about 79 per cent, of the atmosphere. 

 Unlike oxygen, its combining power with other ele- 

 ments is very weak, and when it does so combine 

 the substances formed are very unstable. Nitro- 

 gen, therefore, is one of the chief elements in our 

 explosives. Sulphur, like carbon, is remarkable for 



