CHAPTER VIII. 

 THE URINE. 



THE urine is distinguished from other animal fluids by the fact 

 that it represents the product of physiological disintegration. The 

 various manifestations of force in the living body, such as heat, sen- 

 sibility, and motion, are produced at the expense of its materials, by 

 their metamorphosis in the process of nutrition. The transformation 

 and renewal of its constituents are accordingly essential conditions of 

 its vital activity. Every living being absorbs from without nutritive 

 materials, which are modified by assimilation and converted into the 

 ingredients of its tissues ; and at the same time its elements pass into 

 new forms of combination, to be expelled as the products of disinte- 

 gration. 



Certain substances, therefore, are constantly making their appearance 

 in the body, which were not introduced with the food, but which have 

 been produced by retrograde metamorphosis. They are derived from 

 materials which once formed part of the animal tissues, but which have 

 become altered by internal transformation, and are no longer capable of 

 aiding in the performance of the functions. The elimination and re- 

 moval of these materials is the process of excretion, and the materials 

 themselves are known as excrementitious substances. 



The excrementitious substances are formed for the most part in the 

 tissues, from which they are absorbed by the blood and conveyed to 

 excretory organs by which they are discharged. If their elimination 

 be impeded, their accumulation in the system produces a disturbance, 

 which is more or less severe according to their special character and 

 the rapidity of their production. This disturbing influence is especially 

 manifested in its action upon the nervous system, causing abnormal 

 irritability, derangement of the senses, and, in extreme cases, delirium, 

 insensibility, and death. 



In the normal condition and in normal quantities, the excrementi- 

 tious matters are not poisonous, nor even deleterious ; they are the 

 natural products of functional activity, and therefore as essential to 

 the manifestation of life as the nutritious material supplied by the 

 food. It is only when their elimination is retarded that they interfere 

 with the performance of the functions, by deranging the constitution 

 of the tissues. 



Some of the excrementitious matters produced in the body are prob- 

 ably eliminated, in small proportion, with the perspiration or the feces; 

 and carbonic acid is abundantly exhaled from the lungs. But among 



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