502 OF SECRETION AND EXCRETION. 



substance termed Oxide of Omichmyl by Scharling (which is apparently of 

 a resinous nature), and others. The aggregate amount of the extractives is 

 estimated by Dr. Parkes at 154 grains per diem, and constitutes a wide and 

 very important field for future investigations. It will thus be seen that the 

 total quantity of solid material eliminated by the kidneys does not fall far short 

 of 900 grains in the 24 hours for a healthy adult man weighing 150 Ibs., the 

 proportion of organic compounds being about 550 grains, and of inorganic 

 about 300 grains. Under the head of constituents not constantly, or not cer- 

 tainly present, or perhaps present only in disease, may be enumerated albu- 

 men, fibrin, kreatin, xauthin, sarkiu, grape-sugar, glycin in combination with 

 benzoic acid forming hippuric acid, 1 lactic and oxalic acids, fatty substances, 

 biliary coloring matter, salts of the biliary acids, allantoiu, leucin, and tyro- 

 sin, cystiu, inosite, taurin, hsematin, pus, spermatozoa, carbonate of ammonia, 

 phosphate of ammonia and magnesia, and sulphuretted hydrogen, 2 besides 

 various substances consumed as food and eliminated by the kidneys, as the 

 coloring and odorous matters of various vegetables and certain metals. The 

 acid reaction of the urine depends essentially on the presence of the acid 

 phosphate of soda. 



411. The most important of the organic constituents of the Urine is that 

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

 the secretion, is termed urea. 3 Its chemical relations are stated to be best 

 explained upon the hypothesis that it is the amide of carbonic acid. 4 This 

 substance, as already mentioned ( 197), exists preformed in the blood in 

 the proportion of from 2 parts (in renal venous) to 4 parts (in renal arterial 

 blood) in 10,000. It possesses the power of dialyzing through animal mem- 

 branes with remarkable facility, almost equalling carbonate of potash in this 

 respect. 5 The absolute quantity of urea eliminated in 24 hours, varies with 

 age, season, weight of body, food, and occupation, and has been made a sub- 

 ject of examination by various chemists. The following table 6 gives the 

 results of some of the more recent analyses: 



From an examination of such tables as this we may draw the conclusions, 

 that the average quantity of urea discharged by a man of good bodily health, 

 on full animal diet, is about 500 grains per diem ; and that children of from 

 3 to 7 years of age excrete, proportionately to their weight, about double 

 the quantity of urea per diem excreted by men in adult life, the quantity 

 still further diminishing in old age. The minimum amount excreted by an 

 adult whilst fasting and at rest is about 2 grains per 1 Ib. of body-weight. 

 In infants at the breast Pollack (loc. cit.), found the quantity to vary from 

 15 to 30 grains per diem. 



Season. Dr. Ed. Smith, 7 in the course of the year, found that the daily 

 quantity (in himself) varied from 219 to upwards of 700 grains, the average 



1 Especially in infants at the breast (Pollack, loc. cit.). 



2 v. Gorup-Besanez, Phys. Chemie, p. 510. 



N 2 , contains 46.7 per cent, of nitrogen, and is isomeric with ammo- 



C ) O ) 



mum cyanate, CNNH 4 O = II, \ N 2 , and with carbamide, H 2 y N 2 -f- C0 r 



H, ) II., j 



Miller's Chemistry, vol. iii, p. 615. 

 6 Sec Weikart, Wagner's Archiv d. Heilkundc, 1862, p. 119. 



6 Partly taken from Dr. Day's Physiolog. Chemistry, 1860. 



7 Proceedings of the Royal Society for May 30th, 1861, and a private communica- 

 tion. 



