230 METAMORPHOSIS OF TISSUE. 



proceeding extends itself in organic substances, not merely to the 

 disintegration, step by step, of one atom after the other, but also 

 to the individual atoms of their constituents ; that is to say, it is 

 not, for instance, one atom of sugar after the other which is directly 

 converted into carbonic acid and water, but whilst the separate 

 atoms of hydrogen of the sugar are oxidised, there are formed vari- 

 ous derivatives before we obtain the final results of carbonic acid 

 and water. The length of time which, as Liebig* has shown, is 

 required for the completion of many chemical processes external 

 to, and independent of, the influence of living organisms, makes 

 the gradual and slow course of chemico-vital processes less remark- 

 able than it was formerly supposed to be. In order that we may 

 take our stand on direct observation, we will pass in review the 

 individual constituents of the blood, and briefly consider their 

 relations whilst they are simultaneously subjected to the influence 

 of the free or slightly combined alkalies and of the oxygen at the 

 temperature of the living body. 



We will begin with the organic acids, which readily and in no 

 inconsiderable quantity transude into the blood. Every one who 

 has spent even a short time in a chemical laboratory is aware of the 

 rapidity with which organic acids, or rather the salts which they 

 form with alkalies, begin to decompose when there is an excess of 

 the alkali, even where there is a very slight access of oxygen. Fluids 

 previously colourless become brown ; we generally remark the for- 

 mation of vegetable growths ; and a closer examination shows that 

 products of oxidation, such as succinic acid, &c., are generated. 

 Liebig has even recommended gallic and pyrogallic acids as the 

 best eudiometric agents, owing to the high oxidising capacity 

 exhibited by their alkaline salts. The well-known discovery of 

 Wohler, which has justly excited so much attention, is, therefore, 

 nothing extraordinary, and certainly does not prove that the animal 

 body possesses an altogether special oxidising capacity, equalling 

 in intensity our strongest oxidising agents. The means are 

 precisely the same by which organic acids are consumed both 

 within and without the organism ; the apparent intensity of the 

 oxidising power in the blood is not owing to any special force, but 

 is the mere result of a peculiar complication of circumstances. 



We have, moreover, seen that the carbo-hydrates contained in 

 nutrient matters for the most part reach the blood in the form of 

 grape-sugar. We can hardly wonder at the rapidity with which 



* Ann. d. Ch. u. Fkarm. Bd. 65, S. 350-352. 



