CHAP, nr.] ELIMINATION OF WASTE PRODUCTS. 655 



proteids to trust largely to their behaviour as regards precipitation 

 upon the addition of certain saline bodies; and the presence of 

 saline bodies in the natural urine introduces complications. It 

 would appear, however, that the proteids usually present are seruni- 

 albumin and globulin ; these are not however as a rule, if ever, 

 present in the same relative proportions as in blood-plasma; and 

 either the one or the other may be present by itself. A form of 

 albumose ( 203) called hemi-albumose, is sometimes found, and 

 indeed probably very many distinct kinds of proteids are from 

 time to time present. If egg-albumin be injected into the blood 

 it appears in the urine as egg-albumin, and peptone similarly 

 injected appears as peptone. 



The sugar which is found in the urine of diabetes is un distin- 

 guishable from ordinary dextrose ; but whether it is absolutely 

 identical with that body, or whether the sugar in all cases of 

 diabetic urine is exactly the same, cannot perhaps as yet be 

 regarded as definitely settled. 



When blood is mingled with urine in the kidney and in the 

 urinary passages the constituents of the former are of course added 

 to those of the latter ; and when as sometimes happens chyle from 

 the lacteals makes its way into the kidneys the urine contains the 

 fats and other constituents of chyle. Fats, however, may be present 

 without the urine being distinctly ' chylous.' 



Cholesterin, bile-acids, bile-pigments, and one or other of a 

 large number of bodies arising from a disordered metabolism of 

 the body, such as leucin, tyrosin, acetone (in cases of diabetes), 

 oxalic acid, taurin, cystin and many others are also found more 

 or less frequently ; some of these indeed have been regarded as 

 normal constituents. Besides these the urine serves as the chief 

 channel of elimination for various bodies, not proper constituents 

 of food, which may happen to have been taken into the system. 

 Thus various minerals, alkaloids, salts, pigmentary and odori- 

 ferous matters, may be passed unchanged. Many substances 

 thus occasionally taken undergo, however, changes in passing 

 through the body ; the most important of these, since the changes 

 which they undergo throw light on the metabolic processes of the 

 body, will be considered in a succeeding chapter. 



