THE PROCESS OP OXIDATION. 237 



observations,* that the oxygen in the blood must undergo a change 

 resembling that which it experiences when retained for some time 

 in intimate contact with phosphorus, oil of turpentine, &c. If we 

 fail to recognise the presence of ozonised oxygen in the blood by 

 the ordinary tests, as for instance, iodine of potassium with starch, 

 &c., this is obviously no proof of its absence, for in the presence 

 of a large number of oxidisable matters in the blood, it must neces- 

 sarily disappear almost as quickly as it is formed. The recent 

 investigations in physiology, which seem at length to approximate 

 towards the solution of the mysterious connection between elec- 

 tricity and nervous action, while they hold out a prospect of being 

 able to determine more definitely the phenomena of free electricity 

 in the animal body, render it more than probable, that the oxygen 

 within the living body if not in the blood, at all events in other 

 parts passes into this state of special attractive force, and that in 

 this condition it takes part in the vital processes. At all events 

 we feel that Schonbein's admirable discoveries ought not to be 

 disregarded by physiologists, notwithstanding the obscurity which 

 still appertains to the principles from which we must deduce an 

 explanation of these facts. 



But whatever difference of opinion may exist as to the more 

 immediate relations in which the inspired oxygen combines in the 

 body with individual substances, every one must admit the correct- 

 ness of Liebig's ingenious hypothesis, that the alkalies in the 

 blood promote and maintain the combustibility of the respiratory 

 constituents of the food, and that they consequently serve as 

 essential conditions for the maintenance of animal heat. In the 

 absence of a positive proof of this proposition, we should not wholly 

 reject the negative evidence in its favour. We have often alluded 

 to Wohler's discovery, that organic acids, such as tartaric, citric, 

 and gallic acids, when they had been introduced in a free state into 

 the body, reappeared unchanged in the urine after their passage 

 through the organism, whilst their alkaline salts, under similar rela- 

 tions, are burnt within the body. We cannot surely explain this 

 fact, except by assuming that the presence of the alkali induces, in 

 the one case, the oxidation of the organic acid, whilst in the other 

 case, the free acid, if present in sufficient quantity, suspends the 

 alkalinity of the blood, and consequently also its oxidising capacity, 

 until it is removed from the organism through the kidneys. 



A series of experiments were made some years ago in my 



* Journ. f. pr. Chem. Bd. 52, S. 135-149 u. Bd. 53, S. 321-331. 



