PROBLEMS OF PHYSIOLOGICAL CHEMISTRY. 517 



not to be directly excreted, is further employed in the organism, and 

 exerts an influence on the chemical processes taking place, and may 

 therefore produce disturbances in them. An example will explain 

 this : In a large number of mammals the glycocol formed in the or- 

 ganism is not separated by the kidneys under ordinary circumstances ; 

 but a quantity of benzoic acid taken with the food is sufficient to fix 

 the glycocol with the formation of hippuric acid, and to separate it in 

 this form. These and similar facts, which can be mentioned in large 

 numbers, have a very important signification, for they give the strong- 

 est support to the assertion that the chemical process in the animal 

 body may be considerably changed by apparently slight circumstances. 

 If we accept this, and consider the occurrence of substances still un- 

 known, and present, perhaps, only in very small quantity in the animal 

 organism, we will obtain a hint as to the explanation of effects which 

 many foreign substances produce, though in very small quantities, on 

 the organism. Who does not know the action of strychnia, curarine, 

 prussic acid, and similar poisons ? 



As our knowledge of these poisons has increased, we have found 

 that they never act on the whole organism, but always on particular 

 organs or groups of organs ; these may be the nerves, the muscles, the 

 glands, or only a portion of them. While the curarine paralyzes all 

 voluntary muscles, the heart perceives nothing of its effects ; on the 

 other hand, the poison of the fly-agaric muscarine paralyzes the 

 heart, but not the vohmtaiy muscles. Strychnia acts only on certain 

 portions of the spinal marrow, opium only on parts of the cerebrum ; 

 phenomena which remain completely unintelligible until we attempt 

 to explain them from a chemical point of view, and assume that, at 

 the points accessible to the action of these poisons, there occur, in 

 very small quantities, substances which are of the highest importance 

 to the vital action of the organism, and which are decomposed by 

 them. Of course, chemistry has not yet shown us any essential differ- 

 ence between striped and unstriped muscles, between brain and the 

 spinal marrow, or between the different parts of these organs ; but, as 

 the observation of certain lines in the spectrum has led to the dis- 

 covery of new elements, so may the action of these poisons, at some 

 future time, serve as a guide in searching for these suspected sub- 

 stances. 



The chemistry of the animal body is not simply confined to the 

 formation and decomposition of definite chemical compounds ; the 

 organism also makes use of certain physical phenomena which are 

 inseparably connected with the chemical, namely, the electric and the 

 thermic. The former take part in the excitation of the nerves, per- 

 haps also in some of the chemical processes ; the latter are to be 

 considered as the source of heat in warm-blooded animals as well 

 as of the mechanical force developed by the different muscles. These 

 important facts throw light on the total character of the chemical 



