380 THE UKINE. 



amined. The remainder of the tube is then filled with the sodium 

 hypochlorite solution, the mouth of the tube closed, the fluids well 

 mixed, and the tube then inverted in a shallow glass dish filled with a 

 saturated solution of sodium chloride. The mixture of urine and hypo- 

 chlorite solution remains in the tube ; and as the urea is decomposed, 

 its nitrogen is given off in the gaseous form and collects in the upper 

 closed end of the tube, where its volume may be read off on the scale, 

 after the action has ceased. Every cubic centimetre of nitrogen, thus 

 disengaged, represents 2.5 milligrammes of urea. 



The conditions influencing the quantity of urea produced and dis- 

 charged in the healthy subject during twenty-four hours, are the size 

 and general development of the body, the nature of the food, and the 

 state of rest or activity. Like other products of the living organism, 

 its quantity is in proportion to the entire mass of the body. As a 

 general rule, its daily quantity, in man, is 0.5 per thousand parts of the 

 entire bodily weight ; and for a man of medium size it amounts to about 

 35 grammes per day. As it is a nitrogenous substance, resulting from 

 the final consumption of the albuminous elements of the system, its 

 proportion is greater under a diet of animal food, which is comparatively 

 rich in albuminous matters, than under one of vegetable food, in which 

 these substances are less abundant. Its daily quantity falls to a 

 minimum when the diet is exclusively confined to non-nitrogenous arti- 

 cles of food, namely, starch, sugar, and fat. It is still, however, pro- 

 duced and excreted under an exclusively non-nitrogenous diet, and even 

 when no food whatever is taken, so long as the animal functions con- 

 tinue to be performed. 



The results obtained by nearly all experimenters led to the conclu- 

 sion that the quantity of urea excreted is especially increased by mus- 

 cular exertion , until a doubt was thrown upon this point by Tick and 

 Wislicenus in 1866. These observers ascended a mountain on foot, 

 the ascent occupying a little over eight hours ; during which time, and 

 for seventeen hours beforehand, they confined themselves to a diet of 

 non-nitrogenous food. They found the amount of urea discharged per 

 hour to be less, while engaged in ascending the mountain, than it was 

 before ; but it increased during the following night, after a meal of 

 animal food. 



Subsequent observers have obtained various results. Dr. Parkes, in a 

 series of very careful and extended observations, 1 found that the dis- 

 charge of urea was increased not during, but after, a period of muscular 

 work. This was shown even in a man confined for five days to a non- 

 nitrogenous diet, in whom the discharge of urea was not increased on 

 the day of unusual muscular effort, but on the following day was a little 

 more than doubled. 



The observations of Prof. A. Flint, Jr., on the excretion of urea in 

 the case of the pedestrian Weston, have the important advantage of ex- 



1 Proceedings of the Royal Society of London, vol. xvi. p. 48, and March 2, 

 1871. 



