SECRETION OF URINE. 533 



poisonous operation of the elements of the Urine, upon the several organs 

 whose function is disturbed ; and that many complaints, in which no such 

 agency has been until recently suspected, especially Convulsive disorders 

 arising from a disordered action of the Nervous centres, are due to the in- 

 sufficient elimination of Urea from the Blood. 



671. In order to form a correct opinion of the state of the Urinary secretion 

 in morbid conditions of the system, it is desirable to be acquainted with every 

 leading particular regarding its healthy characters. The average quantity, 

 during 24 hours, has been variously estimated : it differs, of course, with the 

 amount of fluid ingested, and it is influenced also by the external temperature, 

 a much smaller amount of the superfluous fluid of the body being set free 

 from the skin in winter than in summer, and a larger proportion being carried 

 off by the kidneys. Probably we shall be pretty near the truth, in estimating 

 the amount at about 30 oz. in summer, to 40 oz. in winter, for a person who 

 does not drink more than the simple wants of nature require. The Specific 

 Gravity comes to be a very important character, in various morbid conditions 

 of the urine : and it is therefore desirable to estimate it correctly. This also 

 is, of course, liable to the same causes of variation ; since, when the same 

 amount of solid matter is dissolved in a larger or smaller quantity of water, the 

 specific gravity will be proportionably lower or higher. From long and repeat- 

 ed attention to this subject, Dr. Prout is satisfied that the standard Specific 

 Gravity of the Urine of a healthy person in the prime of life, during the whole 

 year in this country, is something less than 1020, ranging from about 1015 in 

 the winter to 1025 in the summer. The urine of Man in health usually ex- 

 hibits an acid reaction ; this depends, however, upon certain conditions fur- 

 nished by the aliment ; and may be altered (as will presently appear) by a 

 change in the ingesta. The following Analysis of Healthy Urine by Berze- 

 lius, is regarded by Dr. Prout as correctly representing its components. We 

 shall presently find, however, that it is dissented from by Liebig, as to several 

 important particulars. 



'a. Water 933-00 



b. Urea 30-10 



c. Lithic acid ........ I'OO 



j C Free lactic acid, lactate of ammonia, and? 17-14 



fl 'C ' ^ animal matters not separable from them 5 



e. Mucus of the bladder 0-32 



' C Sulphate of soda 3-16 



/' ? potash 3-71 



Phosphate of soda 2-94 



1-65 



03 

 |J 



o^i 



ammona 



7 \ Muriate of soda ...... 



*" ammonia ...... 1-50 



C Earthy phosphates, with trace of fluate of lime . 1-00 



' )silex y -03 



1000-00 



672. The most important of all these ingredients is evidently that which, 

 from its being the principal cause of the characteristic properties of the urine, 

 is termed Urea. This may be readily separated from Urine, in the form of 

 transparent colourless crystals ; which have a faint and peculiar, but not 

 urinous odour ; and, as already mentioned, it is distinctly traceable in the 

 Blood, where it rapidly accumulates, if its continual elimination be in any way 

 interfered with. It is very soluble in water, and combines with acids without 

 neutralizing them : in the Human urine it is believed by Dr. Prout to exist 



45* 



