CHAP. XXXIV.] 



REACTION. 



497 



tions, such as sudden joy, or fright, or anxiety, will cause the secretion of 

 urine having a much larger proportion of water than usual. 



All these circumstances, and many others of less importance, have been 

 found to affect the characters of healthy urine ; and, on this account, consider- 

 able difficulty has been felt in attempting to define the precise characters of 

 the secretion in health. Again, the composition of the urine differs at dif- 

 ferent periods of life, but in a much less degree in different individuals at the 

 same period. The urine of men, in the prime of life, contains more solid 

 matter, and less water, than that of old men, women, or children. 



Quantity of Urine. The quantity of urine discharged in the course of 

 twenty-four hours, in a state of health, varies very much, but it may be said to 

 amount to about 30 or 40 ounces. The density varies from 1-010 to 1-020 or 

 1-025 and the quantity of solid matter from 4 or 5 to 8 per cent. The amount 

 of solid matter eliminated from the kidneys of a healthy man who lives well 

 may be roughly stated to be about 1000 grains in twenty-four hours. 



Ee-action. Healthy urine exhibits an acid re-action ; but the intensity of 

 the re-action varies at certain periods of the day. Dr. Bence Jones, who has 

 lately investigated this subject, found that the urine was most acid immedi- 

 ately before meals, and the intensity of the acidity diminishes until five or 

 six hours after the meal. This condition, occurring in the urine secreted 

 soon after digestion, depends upon the quantity of alkali set free in the blood 

 in consequence of the decomposition of certain salts which furnish the acid 

 entering into the composition of the gastric juice. 



The re-action of healthy urine has been attributed to the presence of free 

 lactic acid, and also to 



acetic acid ; but the in- Fig. 242. 



vestigations of Liebig 

 have rendered it proba- 

 ble that it depends, not 

 upon the existence of 

 free or uncombined 

 acid, but upon the pre- 

 sence of certain salts 

 which exhibit a deci- 

 dedly acid re-action, 

 although there is no 

 free or uncombined 

 acid. Such salts are 

 presented to us in the 

 phosphates, which have 

 the property of being 

 very readily changed 

 from the alkaline to 

 the acid, or super-salt. 



After standing for 



some hours, healthy urine deposits a slight precipitate, forming a light 

 flocculent cloud, consisting of vesical mucus, and a little epithelial debris. 

 This deposit is much more abundant in the urine of women, in conse- 

 quence of the admixture of a considerable quantity of vaginal epithelium. 

 Not unfrequently, epithelium from the urethra, or bladder, will be found in 



$*'.' 



a. Various forms of lithic acid crystals, b. Deposit of lithate of 

 soda, amorphous, c. Lithate of soda forming spherules with irre- 

 gular crystals projecting from them. d. Oxalate of lime. e. Dumb- 

 bell crystals of oxalate or oxalurate of lime. 



