36 



LIVING MATTER OR PROTOPLASM. 



All proteids have nearly the same chemical composition and 

 similar physical properties, however different may be the forms 

 of protoplasm in which they occur. The analysis of protoplasm, 

 or rather of the proteids which are its basis, teaches us really 

 nothing of its vital properties, but serves only to show the chem- 

 ical composition of the material basis by which these are mani- 

 fested. 



Proteids are so called from their resemblance to protein (np&)- 

 ros, first], a substance first described and named by Mulder. 

 According to Hoppe-Seyler they have approximately the follow- 

 ing percentage composition : 



A small quantity of phosphorus is also very frequently pres- 

 ent. Associated with these elements are always small quantities 

 of various mineral substances which remain as the ash when pro- 

 toplasm is burned ; but the nature of their relations to the other 

 elements is uncertain. The ash varies both in quantity and 

 chemical composition in different animals and plants. In the 

 white-of-egg the chief constituents of the ash are potassium 

 chloride (KC1) and sodium chloride (NaCl), the former being 

 much in excess. The remainder consists of phosphates, sulphates, 

 and carbonates of sodium and potassium, with minute quantities of 

 calcium, magnesium, and iron, and a trace of silicon. Many other 

 mineral substances occur in association with other kinds of pro- 

 teids, but always in very small proportion. These salts are in 

 some way essential to the activity of protoplasm, as we know by 

 familiar experience. Man, like other animals and the plants, re- 

 quires certain mineral substances (e.g. common salt), but we have 

 no knowledge of the part these play in protoplasm. 



It is important to note the substantial chemical identity of 

 animal and vegetal proteids, because this is one reason for regard- 

 ing vegetal and animal protoplasm as essentially identical in other 

 respects. The following table from Johnson, after Gorup- 

 Besanez and Ritthausen, shows the percentage composition of 

 various proteids, and proves that the difference between vegetal 



