556 Or rank Physics. [July, 



It might be imagined that such a germ would be greatly diver- 

 sified in the character of its molecules. Yet no such necessity 

 exists. The divergence from homogeneity in these molecules 

 would probably be very slight. For diverse as are the physical 

 characters of separate tissues, it is improbable that they vary 

 greatly in chemical character. The protoplasmic bases of all 

 the tissues are perhaps nearly homogeneous, minute differences 

 in their chemical constitution, and in their polar affinities, yield- 

 ing the wide divergence in the physical characters of the tissues. 



The physical analysis of a tree yields us striking evidence on 

 this point. Here we find solidified woody fibers ; there vascu- 

 lar tubes of varied form ; here gum, there cork, there mucilage; 

 here at least two varieties of starch; in the sap dissolved sugar; 

 in the flower and fruit, liquid or solidified sugar, of several varie- 

 ties. In these diverse tissues we have almost all the material of 

 the tree. Yet when we come to examine them chemically we 

 find them to be nearly the same thing. They are all composed 

 of carbon with slightly different equivalents of water. And if the 

 divergent tissues have but this slight chemical difference, how 

 much less may be the differences in the protoplasmic nuclei to 

 whose chemical activity they are due? 



It is probable, therefore, that the protoplasm of the varied ani- 

 mal tissues has but minute differences in its chemical constitution, 

 these minute differences being capable of yielding marked diver- 

 gences in the physical results of their action. And the germ, 

 which must contain molecules derived from every portion of the 

 body, may be a nearly homogeneous mass of protoplasm, the 

 minutest differences in its molecules being capable of yielding 

 marked differences in the tissues arising from them. 



The marvelously intricate germ of the human body is not pro- 

 duced but once, or but a few times. It is, on the contrary, con- 

 tinually produced, as if the body was incessantly employed m 

 forming such minute and generalized copies of itself. For such 

 a continual reproduction there must be some important physio- 

 logical agency constantly affecting every tissue, or perhaps every 

 cell of the body, so that these tissues, in addition to their ordi- 

 nary duty, perform an unceasing generative labor. They are 

 adapted to work not only for the needs of the single individual to 

 which they belong, but for a possibly great number of future in- 

 dividuals, since, could the germs produced by each individual 



