402 PHYSIOLOGY CHAP. 



these originate in the bacterial processes of fermentation and 

 putrefaction which the proteins and carbohydrates undergo in the 

 intestine. The fatty acids of low molecular weight are probably 

 oxidised after their absorption in the blood, while those of higher 

 molecular weight undergo incomplete oxidation only, and are 

 eliminated partly by the lungs, partly by the kidneys. They are 

 more abundant in the urine of the herbivora than in that of 

 carnivora. 



VIII. The question whether normal urine contains sugar or 

 not has been much discussed. It is difficult to clear up this point 

 because certain substances in the urine have, in common with 

 sugar, the property of reducing the oxides of copper and mercury 

 in alkaline solution ; such are uric acid, hippuric acid, creatinine, 

 pyrocatechin. These substances are not, however, like sugar liable 

 to alcoholic fermentation, which is constantly observed when 

 beer yeast is added to urine (Abeles). Nearly every one now 

 believes in the view originally put forward by Briicke, that urine 

 normally contains traces of glucose or dextrose. 



A considerable amount of lactose is present in the urine of 

 women during lactation (Blot, Hofmeister, and others). The 

 physiological and pathological conditions under which the sugar of 

 the urine can be increased temporarily (glycosuria) or permanently 

 (diabetes mellitus), have already been treated at length (Chapter V. 

 p. 314 et seq.). 



According to Landwehr's researches, a carbohydrate similar to 

 dextrin, and non-fermentable, is always present in normal urine : 

 this he termed animal gum. It can be isolated by means of its 

 property of forming an insoluble compound with copper. When 

 boiled with acids, animal gum gives rise to a reducing substance 

 (probably a sugar) which increases the total reducing power of 

 the urine. Wedenski and Baisch confirmed the observations of 

 Landwehr. It is probable that the mother-substance of animal 

 gum is mucin, the chief constituent of the mucus secreted by the 

 epithelia that line the urinary passages, which under normal 

 conditions is present in small quantities in the urine. 



According to v. Jaksch, normal urine always contains a small 

 quantity of acetone or dimetliylketone (C 3 H 6 O), a compound closely 

 allied to the alcohols, which was first discovered in large quantities 

 in diabetic urine by Fetters (1857) and Kaulisch (1860). 



The presence of acetone in normal urine was questioned by 

 Albertoni, le Nobel, and Moscatelli ; but it has been confirmed by 

 others in Italy by Boeri, who regularly found 12-15 mgrms. per 

 diem under physiological conditions. It appears in considerable 

 quantities in diabetics, and under various morbid conditions 

 accompanied by fever ; in different gastro - intestinal affections ; 

 in many pathological or experimental lesions of the nervous 

 system, in various exogenous or endogenous intoxications, in 



