498 OF SECRETION AND EXCRETION. 



is developed ; instead of an acid, an alkaline reaction is presented, in conse- 

 quence of the decomposition of the urea into carbonate of ammonia; and a 

 precipitation of earthy phosphates then takes place. A turbidity may be 

 produced, however, by the precipitation of urates of soda and ammonia, on 

 the simple cooling of the urine, without any such departure from its normal 

 composition as would properly constitute disease, but under some of the con- 

 ditions hereafter to be specified ( 411). But if the urine be turbid when it 

 has first passed from the body, and has a temperature of 98 or 100, it 

 must be considered as abnormal. 



408. Quantity. Dr. Parkes, 1 who has collected the averages of many dif- 

 ferent observers, states that 52^ fluid ounces may be considered to represent 

 the mean quantity of urine discharged in 24 hours by healthy male adults 

 between 20 and 40 years of age. 2 The extremes given by different experi- 

 menters are, 35 ounces (Prout), and 81 ounces (Bocker). Almost every 

 intervening number between these two remarkably different quantities has 

 been stated by one observer or another to be the usual average. Great dif- 

 ferences therefore exist, even in healthy adults; and the amount will vary 

 with the quantity of fluid ingested, the external temperature and consequent 

 activity of the cutaneous transpiration, the nature and quality of the food, 

 the temperament of the body, and perhaps even with national peculiarities. 

 Dr. Ed. Smith, from daily experiments made throughout the year, has shown 

 that during a cold summer (half-year from May to October) the average 

 quantity was somewhat more, whilst during a hot summer it was somewhat 

 less, than during the winter six mouths. With alcohol given to prisoners, 

 there was an average decrease of 20 ounces per day for three days, the quan- 

 tity of water drank being unchanged. With a day of rest the quantity was 

 less than on days of labor, and there was more on treadwheel days, notwith- 

 standing that the quantity of water drank was the same. And there was 

 more perspiration with the hard labor. Women secrete somewhat more urine 

 than meu, :i and children nearly twice as much in proportion to the weight of 

 the body. Some time, however, usually elapses after birth before the kidneys 

 begin to discharge their function with activity, the uriue up to the third day 

 being usually scanty, albuminous, destitute of urea, and containing but a small 

 proportion of solid ingredients. Pollack 4 found that in infants from eight 

 to eighty days of age the quantity of urine discharged varied from 250 to 410 

 cub. cent. (2 to t of a pint) per diem, and that it was almost uniformly acid. 



409. The secretion of urine has been shown by various experimenters, 5 

 and especially by Ustimowitsch, to be the product of two factors, one of 

 which is the difference of pressure between the circulating blood and the ex- 

 creted urine, whilst the other is the amount of urinary material which the 

 blood contains. When the blood-pressure is low the secretion is diminished, 

 and if the pressure fall below 40 mm. of mercury it is entirely arrested ; on 

 the contrary, when the blood-pressure is high, the secretion is augmented. 

 It may be observed, however, that the pressure of the blood in the renal 

 vessels is not always identical with that of the system generally, since, al- 

 though it must necessarily fall when the aortic pressure falls, it may be re- 

 duced considerably below that in the systemic arteries generally, by any 

 cause leading to contraction of the renal arteries. In accordance with this, 

 diminution or arrest of the secretion has been noticed when the blood-pres- 



1 On the Urine, p. 5. 



2 This number agrees very exactly with the careful experiments of Drs. Ed. Smith 

 and Kaupp, Arch. f. Phys. Heilk.. Bd. xiv. 



3 Dondcrs, Physiologic, p. 485. ' 4 Jalirb. f. Kindorheilk., N. F., Bd. ii, p. 27. 

 5 See Bernard, Le9ons, 1859, t. ii, p. 155; Ludwig and Goll, Zeitschrift f. ration. 



JMi'd., Bd. iv,p. 93; Hermann, Vircnow's Archiv, Bd. xxxiv; Ustimowitsch, Lud- 

 wig's Arbeiten, 1870, p. 198. 



