THE URINE. 



329 



The nitrogenous ingredients of the food, during all three periods, 

 were also recorded, so that their influence could be estimated at the 

 same time with that of the muscular exertion. 



The following table gives the main result of these experiments, as 

 connected with the present subject : 



It is evident, therefore, that during unusual muscular exertion the 

 daily quantity of urea was increased by nearly fifteen per cent., the 

 nitrogenous elements of the food being at the same time diminished ; 

 and that the total quantity of nitrogen discharged by the urea and feces 

 combined was more than fifty per cent, greater than that introduced 

 with the food, while in both the previous and subsequent periods it 

 was from seven to fifteen per cent. less. Five years later, observations 

 were made on the same pedestrian by Pavy,* during a six days' walk, 

 averaging 15 miles per day, with similar results; there being an 

 increased discharge of urea, and an increased elimination of nitrogen 

 not accounted for by that taken with the food. 



Great-mine. This substance is closely allied to urea in chemical com- 

 position, but is produced in much smaller quantity ; its total amount 

 not usually exceeding 1 gramme per day. It is probably, like urea, a 

 final product of the metamorphosis of albumenoid matters, but it is no 

 doubt immediately derived from the creatine of muscular tissue, from 

 which it may be artificially produced by the action of heat and dilute 

 sulphuric acid. But little is known with regard to the conditions * 

 which increase or diminish its production in the body. 



Sodium and Potassium Urates. The uric acid of the sodium and 

 potassium urates is a nitrogenous organic acid, belonging to the class 

 of excrenientitious matters. Like urea, it is increased in quantity by a 

 nitrogenous, and decreased by a non-nitrogenous diet ; but its relations 

 to muscular exercise and other temporary conditions are not fully 

 known. The urates are readily soluble in water, and are usually ex- 

 creted to the amount of about 1.T5 gramme per day. The Mppurates 

 are similar in their general physiological relations to the urates, except- 

 ing that they are more abundant under a vegetable diet, and disappear 

 altogether under the exclusive use of animal food. In man, under an 

 ordinary mixed diet, they are about one-half as abundant as the urates. 



Sodium Biphosphate. This is the ingredient which gives to the 



London Lancet, 1876. Vol. ii., p. 848. 



