>> 



15 



COMPOSITION OF PROTOPLASM 5 



The occurrence of these movements is alone sufficient to 

 show that Amoeba is an organism or living thing, and no 

 mere mass of dead matter. 



The jelly-like substance of which Amoeba is composed is 

 called protoplasm. It is shown by chemical analysis 1 

 to consist mainly of certain substances known as proteids, 

 bodies of extreme complexity in chemical constitution, the 

 most familiar example of which is white of egg or albumen. 

 They are compounds of carbon, hydrogen, oxygen, nitrogen, 

 and sulphur, the five elements being combined in the 

 following proportions : 



Carbon . . from 51*5 to 54-5 per cent. 



Hydrogen . 6-9 7-3 



Oxygen 20-9 23-5 



Nitrogen . 15-2 17-0 



Sulphur . ,, 0*3 ,, 2*0 ,, ,, 



Besides proteids, protoplasm contains small proportions 

 of mineral matters, especially phosphates and sulphates of 

 potassium, calcium, and magnesium. It also contains a 

 considerable quantity of water which being as essential a 

 constituent of it as the proteids and the mineral salts, is 

 called water of organization. 



Protoplasm is dissolved by prolonged treatment with weak 

 acids or alkalies. Strong alcohol coagulates it, />., causes it 

 to shrink by withdrawal of water and become comparatively 

 hard and opaque. Coagulation is also produced by raising 

 the temperature to about 40 C. ; the reader will remember 

 how the familiar proteid white of egg is coagulated and 

 rendered hard and opaque by heat. 



1 Accurate analyses of the protoplasm of Amoeba have not been 

 made, but the various micro-chemical tests which can be applied to it 

 leave no doubt that it agrees in all essential respects with the protoplasm 

 of other organisms, the composition of which is known (see p. 7). 



