METHODS OF PHYSIOLOGICAL RESEARCH 43 



that certain substances found exclusively in the living organism 

 cannot be produced chemico-physically, but arise only through the 

 working of the vital force. But, as has been seen (p. 23), in the 

 year 1828, Wohler weakened this once so powerful support 

 for the vitalistic creed by manufacturing synthetically in his 

 laboratory urea, a body which ordinarily is produced only in the 

 metabolism of the living organism. He obtained this from 

 ammonium cyanate, (NH 4 )CNO, which is isomeric with urea 

 (NH 2 ) 2 CO, i.e., possesses the same number of the same atoms in a 

 different arrangement. But ammonium cyanate is manufactured 

 out of purely inorganic materials. This synthesis of urea has 

 been followed by others of equal importance, all of which go to 

 show that characteristic substances belonging to the organism 

 may be compounded artificially. The assumption of a special vital 

 force for their production in the organism is thus rendered super- 

 fluous. Of course it has not yet been possible to manufacture a 

 great number of substances belonging to the animal and the plant 

 body. Indeed, the most important of these substances, proteids, 

 have thus far resisted artificial production in the laboratory, but 

 the reasons for this are evident. The exact chemical composition 

 of proteids is not yet known ; we know what atoms are con- 

 tained in them, but we have no idea how these atoms are joined 

 together. Accordingly it is evident that success in the attempt 

 to manufacture proteids artificially ought not yet to be expected. 

 A second reason is that thus far we have no correct idea of the 

 chemico-physical conditions under which these substances arise in 

 the organism ; and chemistry has recently shown very clearly 

 that the inauguration of a chemical process depends not only 

 upon the presence of the necessary substances, but also upon 

 the fulfilment of certain other conditions. Thus, it has been 

 found that many chemical transformations that do not take place 

 in a large space, occur very easily in capillary spaces under other- 

 wise like conditions, and vice versa. An example long known is 

 the union of oxygen and hydrogen in the spongy-platinum of 

 Dobereiner's lamp. It is known that hydrogen streaming out of a 

 tube into the air does not spontaneously unite with the oxygen of 

 the air ; but, if it pass into the fine pores of platinum-sponge, the 

 union takes place at once, and the hydrogen burns with a luminous 

 fiame to form water. Such processes are termed condensations. 

 It is known also that many chemical processes take place only 

 when the substances involved are present in large quantity 

 a phenomenon which as mass-effect plays an important 

 role not only in the laboratory but also, as already demon- 

 strated, in the animal body. Recently, Preyer and Wendt 

 ('91) have suggested the presence of condensation -processes and 

 the absence of mass-effect in capillary spaces as a reason why in the 

 organism, where capillary spaces exist in the cells and their 



