INORGANIC CONSTITUENTS OF THE URINE 347 



Fatty Matters. Fat and fatty acids are said to exist in the normal 

 urine in certain quantity. Their proportion, however, is small, and the 

 mere fact of their presence, only, is of physiological interest. 



Inorganic Constituents of the Urine. It is by the kidneys that the 

 greatest quantity and variety of inorganic salts are discharged from the 

 organism ; and it is probable that even now physiological chemists are 

 not acquainted with the exact proportion and condition of all the 

 constituents of this class found in the urine. In all the processes of 

 nutrition it is found that the inorganic constituents of the blood and 

 tissues accompany the organic matters in their various transformations, 

 although they are themselves unchanged. Indeed, the condition of 

 union of inorganic with organic matters is so intimate that they can not 

 be completely separated without incineration. In view of these facts, 

 it is evident that a certain proportion, at least, of the inorganic salts of 

 the urine is derived from the tissues, of which, in combination with 

 organic matters, they have formed a constituent part. As the kidneys 

 frequently eliminate from the blood foreign matters taken into the 

 system, and are capable sometimes of throwing off an excess of the 

 normal constituents which may be introduced into the circulation, it can 

 readily be understood how a large proportion of some of the inorganic 

 constituents of the urine may be derived from food. 



Chlorides. Almost all the chlorin in the urine is in the form of 

 sodium chloride, the quantity of potassium chloride being insignificant 

 and not of any special physiological importance. By reference to the 

 table of the composition of the urine, it is seen that the proportion of 

 sodium chloride is subject to great variations, the range being between 

 three and eight parts per thousand. This at once suggests the idea 

 that the quantity excreted is dependent to a considerable extent qn the 

 quantity taken in with the food; and, indeed, it has been shown by 

 direct observations that this is the fact. The proportion of sodium 

 chloride in the blood seems to be tolerably constant; and any excess 

 that may be introduced is thrown off chiefly by the kidneys. As the 

 chlorides are deposited with the organic matters in all the acts of nutri- 

 tion, they are found to be eliminated constantly with the products of 

 katabolism of the nitrogenous parts, and their absence from the food 

 does not completely arrest their discharge in the urine. By suppressing 

 salt in the food, its daily excretion may be reduced to between thirty 

 and forty-five grains (1.9 and 2.9 grams). This quantity is less than 

 that ordinarily contained in the ingesta, and under these conditions there 

 is a gradual diminution in the general nutritive activity. In nearly all 

 acute febrile disorders, the chlorin in the urine rapidly diminishes and 

 frequently is reduced to one-hundredth of the normal proportion. The 



