80 ANIMAL CHEMISTRY LECTURE IV. 



The actual occurrence of these particular actions is quite un- 

 proven ; but that some such actions take place is rendered highly 

 probable by a variety of considerations. Thus, in the gradual 

 development and ripening of the olive, we find certain vegetable 

 acids replaced by mannite, and at a later stage this mannite itself 

 replaced by the less oxidised and more complex oleine. (De Luca.) 

 (85.) Again, the compounds formed in one organ of a plant are 

 known to be transferred, in a more or less altered form, to other 

 ^ organs, in which they become accumulated ; and it is not im- 

 probable that certain vegetable products of deoxidised carbonic 

 acid and water may have undergone a partial reoxidation, or even 

 several alternate reoxidations and deoxidations, in the course of 

 their history. Similarly in animals, although the ultimate process 

 is one of oxidation, we know that in certain proximate principles 

 of food the oxidation of some of their constituents is effected at the 

 expense of the remainder, which consequently became deoxidised ; 

 and it is possible that some animal products may have undergone 

 an entire deoxidation, or even several alternate deoxidations and 

 reoxidations, before their final discharge from the body. On all 

 these points very much yet remains to be learned ; but still, the 

 general position holds good, that vegetables effect a simultaneous 

 deoxidation and intercombination of carbon molecules, while ani- 

 mals conversely effect their simultaneous reoxidation and separa- 

 tion. In many instances, also, the representatives of certain stages 

 of building up and breaking up, in vegetable and animal life 

 respectively, are closely allied to, or even identical with, one 

 another. Oxalic acid, for instance, the simplest product of 

 vegetable synthesis, and a frequent constituent of both the highest 

 and lowest vegetable organisms, may be formed, as we have just 

 seen,\)y a deoxidation of carbonic acid. But it also occurs abun- 

 dantly in animal juices and secretions, not as a product of the 

 deoxidation of carbonic acid, but as the last intermediate stage in 

 the oxidation or downward transformation of more complex bodies 

 into carbonic acid ; just as the oxalic acid of commerce is ob- 

 tained from sugar by a process of oxidation which, if carried too 

 far, yields little else than carbonic acid. Benzoic acid, again, 



