PROTOPLASM 1 1 



17. Chemical Composition of Protoplasm. It is impossible to make a satis- 

 factory chemical analysis of protoplasm, as it loses its characteristic powers and 

 probably undergoes important chemical and physical changes in the act of analysis. 

 The dead material thus obtained is no longer the substance with which we started, 

 either as to its power or its structure. The experiment shows, however, that the 

 substance is both chemically and physically unstable. By an analysis of the dead 

 protoplasm, we find present several complex organic compounds, known as proteids, 

 carbohydrates (starches and sugars), fats, ferments, pigments, etc. In addition to 

 these are simpler inorganic compounds, as water and various salts. Doubtless 

 some of these materials are food-substances on their way to form protoplasm, and 

 others are the waste-products of protoplasmic disruption, ready to be cast out of 

 the cell. The proteids are the most complex of all these substances and it is 

 believed that protoplasm finds its real basis in these. 



The proteids are various in composition and properties, but agree in that their 

 molecules contain carbon, hydrogen, oxygen, nitrogen, and sulphur, in proportion 

 roughly as follows: C 53%, O 22%, N 17%, H 7%, S i%. Qarboji is thus the 

 most important single constituent element. The white of egg, the fibrin of the 

 blood, and casein in milk are examples of proteid. 



Carbohydrates consist of C, H, and O. The latter elements are always present 

 in the ratio in which they are represented in water (H 2 0), 'e.g. CeHioOs. The 

 starches, sugars, and cellulose, such as is found in cotton fibres, are illustrations. 



The fats contain the same elements as starch, but the percentage of oxygen 

 in terms of the hydrogen is much smaller than in the starches. 



The ferments are complex organic substances which have the power of produc- 

 ing important chemical changes in other substances without being themselves 

 consumed. They play an important, but not thoroughly understood, r61e in the 

 activities of the organisms, both within and outside the cells which produce them. 

 The active principle of the digestive juices, as ptyalin and pepsin, are examples of 

 ferments which have been extruded from the cells. 



Water (H 2 O) is very important in both the chemical and physical structure of 

 protoplasm. It is very variable in amount, and the degree of activity of the 

 protoplasm is roughly proportional to the amount of water present. Traces of 

 inorganic salts, compounds of chlorine, potassium, sodium, calcium, phosphorus, 

 iron, etc., are also found in solution in the water. 



Most of these substances cannot be considered as "living." The water and 

 inorganic salts and starch cannot be. The starches and fats and urea are organic 

 but not living, If any particular substances are alive it would seem to be the 

 proteins. It may be, however, that life is the result of the intimate relations and 

 interactions of all these various substances rather than a property of any one of 

 them. 



1 8. The Physical Structure of Protoplasm. This varies 

 much from time to time. On account of differences in the 

 amount of water present, the consistency of protoplasm may 

 vary from the quite fluid condition found in actively growing 

 parts, to the very much more solid condition apparent in dry 

 seeds and in the resting or encysted stage of some animals. 



