436 THE URINE. 



Prof. Chittenden concludes his admirable paper in the follow- 

 ing" language : 



" In man uric acid has a twofold origin ; one portion, coming 

 from the breaking down of nuclein-containing tissues or cell- 

 elements of the man's own body, and hence is of endogenous 

 origin, while the other portion usually the larger is of exogen- 

 ous origin, coming from the transformation of free and combined 

 purin compounds present in the food. The uric acid of endogen- 

 ous origin is essentially constant in amount for the same indi- 

 vidual under all conditions of diet, but is subject to slight varia- 

 tion in connection with alterations in the activity of the tissues. 

 Changed conditions embodying increased katabolism of the tissue- 

 elements, increased breaking down of cells and cell-nuclei, might 

 naturally be expected to cause slight alteration in the amount of 

 endogenous uric acid, but analytic results at present do not justify 

 belief in any profound changes in the uric acid output due to this 

 cause. The amount of endogenous uric acid is, therefore, a 

 physiologic constant for a given individual, and, as might be ex- 

 pected, decided variations are to be found in the value of this 

 constant for different individuals. In other words, personal idio- 

 syncrasy, constitutional differences, etc., may manifest themselves 

 in the amount of endogenous uric acid produced. Such a condition 

 of things is by no means strange or out of harmony with physio- 

 logic laws. There is a personality in every man, internal as well 

 as external, and the individual constancy in endogenous uric acid 

 production is merely another illustration of the general truth of 

 this law. Individual functional peculiarities are as liable to 

 existence as personal peculiarities of form and structure. 



" The amount of exogenous uric acid produced in the body is 

 dependent mainly upon two factors, viz., the quantity and char- 

 acter of the nucleins contained in the ingested food, and the 

 quantity and character of the free purin bases present in the food. 

 The nucleins owe their influence solely to the combined purin 

 bases they contain, and since nucleins from different glands and 

 tissues differ both in the amount and character of the purin bases 

 present in their molecules, it follows naturally that the individual 

 nuclein-containing foods have different values as sources of exogen- 

 ous uric acid. Further, since all nucleins are somewhat slowly 

 attacked by the digestive fluids, it follows that the uric acid 

 coming from this source does not appear at once in the urine, but 

 is found some hours after digestion has been under way. The free 

 purin bases, on the other hand, such as are contained in meats, 

 meat-juice, meat-extracts and soups, coffee, cocoa, etc., lead to a 

 quicker output of uric acid, owing to their ready solubility and 

 availability. Differences in the extent of this form of exogenous 

 uric acid production, however, are traceable to differences in the 

 nature of the free purin bases ; adenin, hypoxanthin, and guanin, 



