ON THE PHYSICAL BASIS OF LIFE 97 



plasm, and its activity differs in detail, rather than in prin- 

 ciple, from that of the protoplasm of the nettle. Under 

 sundry circumstances the corpuscle dies and becomes dis- 

 tended 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 he 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 distinguishable 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 ao-o-regation. 



Thus a nucleated mass of protoplasm turns out to be 

 what mav be termed the structural unit of the human bodv. 

 As a matter of fact, the body, in its earliest state, is a mere 

 multiple of such units; and in its perfect condition, it is a 

 multiple of such units, variously modified. 



But does the formula which expresses the essential struc- 

 tural character of the highest animal cover all the rest, as 

 the statement of its powers and faculties covered that of 

 all others? Very nearly. Beast and fowl, reptile and fish, 

 mollusk, worm, and polype, are all composed of struc- 

 tural units of the same character, namely, masses of proto- 

 plasm with a nucleus. There are sundry very low ani- 

 mals, each of which, structurally, is a mere colourless blood- 

 corpuscle, leading an independent life. But, at the very 

 bottom of the animal scale, even this simplicity becomes 

 simplified, and all the phenomena of life are manifested 

 by a particle of protoplasm without a nucleus. Nor are 

 such organisms insignificant by reason of their want of 

 complexity. It is a fair question whether the protoplasm 



