640 



OF SECRETION. 



ence of the components of the secretion in the Blood, is strengthened by the 

 fact that, even in the healthy state, Urea may be detected in the blood ; it only 

 exists there normally, however, in very small quantity; but, when there is 

 any impediment to its excretion, it goes on accumulating, and produces conse- 

 quences more or less serious in proportion to its amount. It is not improba- 

 ble that, as in the case of the retention of Bile in the Blood ( 832), many of 

 the minor as well as of the severer forms of sympathetic disturbance, connected 

 with disordered secretion from the Kidney, are due to the directly poisonous 

 operation of the elements of the Urine, upon the several organs whose func- 

 tion is disturbed ; and that many complaints, in which no such agency has 

 been until recently suspected, especially Convulsive affections arising from 

 a disordered action of the Nervous centres, are due to the insufficient elimi- 

 nation of Urea from the Blood. 



843. 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 from 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 

 Avater, the specific gravity will be proportionally lower or higher. The 

 average, according to Dr. Prout, in a healthy person, taking the whole year 

 round, is about 1020; the standard rising in summer (on account of the greater 

 discharge of fluid by perspiration) to 1025 ; and being lowered in winter to 

 1015. Simon, however, states the average specific gravity at no more than 

 1012. It will depend, in each individual case, upon the amount of fluid habitu- 

 ally ingested, as compared with that dissipated by cutaneous exhalation ; and 

 it will also vary with the period that has elapsed since the last introduction of 

 liquid into the stomach. From these and other causes, the proportion of solid 

 matter in 1000 parts of Urine may vary from 20 to 70. The following table 

 expresses the relative amounts of the different components, in every 100 parts 

 of this solid matter ; according to the analyses of different Chemists. 



Urea ..... 



Uric Acid ..... 

 Extractive matter, Ammonia-salts, ) 

 and Chloride of sodium jj 



Alkaline Sulphates 

 Alkaline Phosphates 

 Phosphates of Lime and Magnesia 



Berzelius. 

 . 45-10 

 1-50 



. 36-30 



. 10-30 



, 6-88 



1-50 



Lehmann. 

 49-68 

 1-61 



Simon. 



33-80 



1-40 



28-95 42-60 



11-58 

 5-96 

 1-97 



8-14 

 6-50 



1-59 



Marchand. 

 48-01 

 1-59 



32-49 



10-18 

 4-57 

 1-S1 



We shall presently find the causes of some of these variations in the nature 

 of the ingesta, and in the amount of exercise taken by the individual. The 

 Urine in health usually exhibits an acid reaction; this depends, however, 

 upon certain conditions furnished by the aliment; and may be altered (as will 

 presently appear) by a change in the ingesta. 



844. The. most important of the above ingredients (constituting from one- 

 third to one-half of the whole solid matters of the Urine) is evidently that 

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



