I. ELEMENTS OF COMPOSITION. 



CHEMICAL investigation has gradually brought under our notice a number 

 of bodies, some organic and some inorganic, which enter into the 

 formation of the human frame as elements of composition. Owing to 

 the rapid progress of science the tale of these increases year by year. 



But these bodies are by no means laid down once for all in the 

 organism to belong to the latter for the whole term of its existence, and 

 to form permanent constituents of its fluid and solid portions. On the 

 contrary, the material of which the animal body is composed is subject 

 to continuous change, to constant transformations, or, in other words, is 

 incessantly coming and going. 



The substances of which our body is made up those, namely, entering 

 into the formation of tissues consist, together with water and other 

 mineral matters, of certain groups of organic principles. These are the 

 albuminous, or, as they are called, the "protein substances," and the nearer 

 derivatives of the same, especially the glutin-yielding and elastic materials, 

 with fatty matters and pigments. Thus we observe that the number of 

 chemical compounds of which our frame is made up is primarily but 

 small. 



But owing to the fact that these do not continue long in their original 

 condition, but undergo decay and metamorphosis, and must in conse- 

 quence be changed, we have an extensive series of chemical mutations 

 bound up with the exitus of matter. We need not be surprised, then, 

 if, out of this limited number of histogenic substances, a whole host of 

 mutation or decomposition products takes its rise. The introduction 

 also of new material to make up for waste likewise introduces many 

 chemical metamorphoses. 



In considering, then, the elements of composition, all these points 

 must be borne in mind. It belongs to the province of histochemistry 

 to show .by what processes alimentary matters are ultimately converted 

 into the constituents of organs and tissues, or, in other words, to follow 

 up the formation of histogenic substances. Again, it must deal as far as 

 possible with the question as to the nature of the numerous products of 

 decomposition. It should demonstrate also how and by what chemical 

 processes the latter spring from histogenic substances ; what is the rela- 

 tion of one to the other; how one mutation product takes its origin 

 from another; and what part each plays in the occurrences of the 

 economy, until it is finally cast out of the system. In this way only 

 could we acquire a satisfactory knowledge of the chemical constitution 

 and decay of our body. 



But, unfortunately, the state of science at the present day does not 

 admit of all these requirements being satisfied in the remotest degree. 



