HI ON THE PHYSICAL BASIS OF LIFE 130 



comparatively small number of colourless cor- 

 puscles, of somewhat larger size and very irregular 

 shape. If the drop of blood be kept at the 

 temperature of the body, these colourless cor- 

 puscles will be seen to exhibit a marvellous activity, 

 changing their forms with great rapidity, drawing 

 in and thrusting out prolongations of their sub- 

 stance, and creeping about as if they were inde- 

 pendent organisms. 



The substance which is thus active is a mass of 

 protoplasm, and its activity differs in detail, rather 

 than in principle, from that of the protoplasm of 

 the nettle. Under sundry circumstances the cor- 

 puscle dies and becomes distended into a round 

 mass, in the midst of which is seen a smaller 

 spherical body, which existed, but was more or 

 less hidden, in the living corpuscle, and is called 

 its nucleus. Corpuscles of essentially similar 

 structure are to be found in the skin, in the lining 

 of the mouth, and scattered through the whole 

 framework of the body. Nay, more ; in the 

 earliest condition of the human organism, in that 

 state in which it has but just become distinguish- 

 able from the egg in which it arises, it is nothing 

 but an aggregation of such corpuscles, and every 

 organ of the body was, once, no more than such 

 an aggregation. 



Thus a nucleated mass of protoplasm turns out 

 to be what may be termed the structural unit of 

 the human body. As a matter of fact, the body, 



