I 



26 PROTOPLASM AND THE CELL 



most important indeed, "dead protoplasm" is a contradiction in terms,, 

 and protoplasm when it has died, whatever that means, is no ] onger 

 protoplasm but only a mass of matter hastening toward decomposition. 

 We may be almost sure that it is then quite unlike, in its essentials of 

 chemical structure, the composition of the same substance when alive. 

 This problem of the analysis of protoplasm is, indeed, difficult, for when 

 one applies any of the methods and reagents of analysis now known, the 

 mass of protoplasm or biogen is forthwith no longer living but dead, and,, 

 therefore, changed in those very respects about which the chemist and the 

 physiologist seek to learn. Here, again, is a field for shrewd hypothesis 

 a field that" has been well cultivated, as almost any physiological 

 chemistry will show. It begins to be obvious that by synthesis, rather 

 than by analysis, the composition of protoplasm will be learned. 



ELEMENTS. Of the chemical "elements," numbering about eighty, 

 there are a dozen which seem to be present without exception in all 

 protoplasm, primal and differentiated. These twelve, a most important 

 list, are carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, chorine r 

 sodium, potassium, calcium, magnesium, and iron. Besides these there 

 are others less universally constant in biogen namely, silicon, fluorine? 

 iodine, bromine, aluminum, manganese, and copper. 



COMPOUNDS. So far in describing the chemical composition of pro- 

 toplasm we have glanced mostly at the raw materials out of which 

 protoplasm is evolved. It would be more satisfactory if, using these as 

 building-stones, we could build in description all the details and marvellous- 

 structures which we know, from the numberless intricate functions 

 which each particle of protoplasm includes. But this cannot as yet be 

 done, and we must be content if we are told with some degree of certainty 

 the principal features of the protoplasmic structure and the functional 

 relations of these to each other and to the phenomena of life in general. 

 (See chapters on Food and Nutrition.) 



The most abundant compound present in primal or undifferentiated 

 protoplasm, and in most of the animal tissues evolved therefrom, is water.. 

 Life is characterized principally by motion, and free and varied motion 

 depends directly on the lability, the ease of movement, of the material.. 

 We know protoplasm as a liquid substance. The red -muscle flesh of the 

 ox seems solid enough to the unaided eye, but carefully examined with 

 a microscope or with reagents every component particle is seen to be a 

 complicated cell filled with a thin fluid, lymph, which is at least 96 per 

 cent, water. Even the bones are 12 or 15 per cent, water, and the tough 

 and solid-looking ligaments connecting them, 77 per cent. Water is the 

 universal solvent in nature, organic as well as inorganic. As Hoppe- 

 Seyler says, "All organisms live in the water," for those which do not live 

 literally under water have nearly all their organs composed of it and 

 surrounded by it, and continue their being and functioning only through 

 its means. "Organisms live not only in water, but in flowing water," the 

 force of which statement will be fully realized later when the rapidity and 

 ubiquity of the blood-lymph circulation is appreciated. Practically the 



