196 ORIGIN OF ORGANIC MATTER 



activity beyond the final generation of dextrin and similar neutral 

 carbo-hydrates. 



In addition to these substances, we find many which are widely 

 distributed in the vegetable kingdom, and contain far less oxygen 

 than the carbo-hydrates ; as, for instance, the oleaginous fats, wax 

 and resins, and several which are entirely without oxygen, that is 

 to say, a large number of ethereal oils, caoutchouc, &c. When, 

 moreover, we perceive that oxygen is given off, whilst carbonic 

 acid is taken up, it would seem as if the developed oxygen were 

 the combined result of the quantities of the gas yielded by several 

 very different substances. Several phyto-physiological facts seem 

 to indicate that the vegetable fats and wax are especially generated 

 from the carbo-hydrate known as starch, whilst daily experience 

 proves that those ethereal oils, which are either deficient in oxygen 

 or entirely without that substance, can only be produced under 

 the prolonged action of solar light. It is, therefore, not only 

 not impossible, but even in some degree probable, that a number 

 of different processes of deoxidation which extend to substances 

 which have previously been more or less freed from oxygen, are 

 simultaneously called into activity under the influence of solar 

 light. Do differently constituted cells co-operate in these various 

 reductions ? Is it only one, or are there several matters which, 

 under the influence of light, effect the elimination of oxygen from 

 highly oxygenous substances ? These, and numerous other ques- 

 tions of a similar nature, force themselves upon our notice, but, 

 unfortunately, in the present state of our knowledge, they do not 

 admit of satisfactory replies. 



In considering the processes of deoxidation, which are con- 

 nected with the life and growth of plants, we should bear in mind 

 that some instances may occur in which the deoxidation is accom- 

 panied by a development of carbonic acid instead of a separation 

 of oxygen. Liebig long since noticed during the prosecution of his 

 experiments on fermentation, putrefaction, and decomposition, 

 that oxygen was taken up by the organic substances during some 

 of these processes of decomposition, and that then several atomic 

 groups of carbonic acid were liberated from this combination. It 

 depends entirely upon the relations existing between the oxygen 

 that is absorbed and the carbonic acid which is developed, whether 

 the remaining substance is richer or poorer in oxygen than the 

 original body. If the volume of oxygen which is added be less 

 than that of the carbonic acid which is evolved, the remaining 

 org nic body will be less oxidised, and will therefore appear 



