8 GENERAL ZOOLOGY 



substance which has never been synthesized. Chemical analysis 

 shows that it contains carbon, hydrogen, nitrogen, oxygen, sul- 

 phur, phosphorus, and sometimes iron. Fats and carbohydrates 

 contain carbon, hydrogen, and oxygen, but in different propor- 

 tions and combined in different ways. Starches and sugars are 

 examples of carbohydrates. Extractives include substances like 

 urea, CO(NH 2 )2, creatinine, C4H7N3O, inosite, C 6 H 6 (OH) 6 , all of 

 which are soluble in water by means of which they can be 

 extracted from coagulated protoplasm. 



The substances making up protoplasm are determined by 

 chemical analysis, which gives but little more than the percentage 

 composition of these constituents. Such an analysis shows that 

 protoplasm is made of chemical elements of common occurrence 

 in inorganic nature and also that there is no chemical element 

 peculiar to protoplasm. Such a simple analysis throws little 

 light on how the chemical elements are combined. For example, 

 the amount of water in a sample of protoplasm is determined by 

 driving off the water by means of heat; the difference in weight 

 before and after representing the percentage of water. Thus 

 by this method mammalian meat is found to contain 76 parts by 

 weight of water. If the same piece of tissue is reduced to ash by 

 incineration, the weight of the residue represents the total of 

 inorganic salts which in this case is about 1 per cent of the whole. 

 Other methods show that this same kind of tissue is composed of 

 21.5 per cent of nitrogenous material and 1.5 per cent of fat. 

 The real problem is to explain how these various components are 

 combined in protoplasm. Certainly the inorganic salts and 

 organic substances are not present as such in living matter but 

 are combined in a chemical complex along with the water in a very 

 intricate manner. If we are to look upon protoplasm as a form 

 of physicochemical system, it differs from other systems in its 

 internal atomic or molecular organization. In other words, the 

 difference between protoplasm and other chemical combinations 

 is not in the chemical elements concerned but in the manner in 

 which they are combined chemically and physically. A random 

 mixture of constituents in the proportions and concentrations 

 as determined by a chemical analysis of protoplasm would not 

 produce a system having the properties of living matter. In 

 order to produce a living system, what is required in addition is a 

 knowledge of the structure or arrangement and the physical state 



