168 BASIC BODIES. 



found substances from which he could produce urea artificially. 

 We must therefore assume that these substances, as creatine and 

 probably inosic acid, are decomposed in the blood, by the action 

 of the alkalies and of free oxygen, into urea and other matters to 

 be excreted. Moreover, my experiments showing that the super- 

 fluous nitrogenous food which enters the blood, and the fact that 

 caffeine, glycine, (Horsford) uric acid, and alloxantin, (Wohler and 

 Frerichs*) soon after they have been taken, perceptibly increase the 

 amount of urea in the urine, support the view that urea is formed in 

 the blood. It is impossible to suppose that this nitrogenous food 

 is first converted into tissue, and subsequently into urea^ &c., for 

 we cannot think that a process occurs here, analogous to that exhi- 

 bited by the percussion -apparatus of Physicists, where a certain 

 number of parts, effecting a percussion, give rise to the repulsion 

 of an equal number of parts. Hence the conversion of this matter 

 can occur in no other place than in the circulating blood, and 

 therefore it is here that the urea must be formed. 



That the urea is formed from nitrogenous matters could not be 

 doubted, even if it did not contain nitrogen (and that in so large a 

 quantity) ; for it is especially after the use of highly nitrogenous 

 food that we find an augmentation of its quantity in the urine. If, 

 however, we should further inquire from what substances is it 

 produced, and what tissues principally contribute to its formation ? 

 we could not, in the present state of our knowledge, give any 

 satisfactory answers to these questions. All that we know is, that 

 urea is a very general product of the decomposition of nitrogenous 

 matters, both naturally within the animal body, and artificially in 

 the laboratory of the chemist. We have already said enough to 

 show that urea is so common a product of the decomposition of 

 nitrogenous bodies, that we could hardly any longer enumerate it 

 among true organic substances, if we tried to establish a distinction 

 between organic and inorganic matter. Moreover, when we treat 

 of uric acid we shall show that, in all probability, a great part of 

 the urea separated by the kidneys from the blood is the product of 

 the decomposition of that acid. 



What is the importance of urea in the fluids of the eye, and 

 whether it has any importance, are questions which, at present, 

 cannot be answered. 



* Ann. d. Ch. u. Pharm. Bd. 65, S. 337-8. 



