264 PRACTICAL PHYSIOLOGY 



first one, separates out. This corresponds to the ethereal sulphates, 

 which have been decomposed by boiling with the acid. 



To determine the total sulphates, it is, therefore, necessary to boil 

 the urine with hydrochloric acid before adding the barium salt. 



The organic radicles with which the acid combines are chiefly phenol 

 and indoxyl, which, it will be remembered, are produced in the intestine 

 by the action of bacteria on proteids. Only a fraction of these is 

 absorbed into the blood, where, on account of the fact that they are 

 poisonous, they are at once combined with sulphuric acid to form an 

 acid salt, and this then combines with the alkalies to form a neutral 

 salt which is non-poisonous, and is excreted as such in the urine. The 

 excretion of these ethereal sulphates becomes enormously increased 

 where excessive bacterial digestion is taking place in the intestine e.g. 

 in intestinal obstruction, typhoid fever, etc. (See Advanced Course, 

 p. 452.) 



Carbonates. These are never found in the acid urine of a normal 

 diet, but if the diet be purely vegetarian, and as a consequence the 

 urine react alkaline, they occur in considerable amount. They are 

 detected by the fact that they cause the urine to effervesce on the 

 addition of a mineral acid. They are derived from the carbonates 

 and organic acids contained in vegetables. They are usually combined 

 with the alkalies, but if they should be combined with the alkaline 

 earths they cause a cloudiness in the urine. 



URINARY DEPOSITS. 



As it is voided the urine is quite clear, but, on standing some time, a 

 sediment usually separates out, and this varies somewhat under different 

 conditions. 



Acid urine from a healthy person may deposit the following : 



1. Urates (see p. 256). The sediment has a chalky appearance and 

 is usually tinged reddish. It disappears on warming the urine. 

 Examined microscopically it is generally amorphous quadriurates but 

 may show a crystalline structure acid urates usually as needles, or 

 as balls with spines projecting from them (Fig. 157). 



2. Uric Acid. This may be split off from the urates as described 

 on p. 258. It appears as a cayenne pepper-like sediment, and has a 

 definite crystalline appearance under the microscope (Fig. 156). The 

 crystals may vary much in shape, but are always large and tinged a 

 reddish colour. The most usual shapes for the crystals to assume are 

 "sheaves,"" whetstones," "rhombic tables," and sometimes "dumb- 

 bells." The presence of the crystals does not necessarily indicate an 



