CHAPTER VI. 



MECHANISM OF THE FORMATION AND DISCHARGE OF TJEINE. 



Formation of the excrementitious constituents of the urine in the tissues, 

 absorption of these principles by the blood, and separation of them from 

 the blood by the kidneys Effects of removal of both kidneys from a liv- 

 ing animal Effects of tying the ureters in a living animal Extirpation of 

 one kidney Influence of blood-pressure, the nervous system, etc., upon 

 the secretion of urine Effects of the destruction of all the nerves going 

 to the kidneys Alternation in the action of the kidneys upon the two 

 sides Changes in the composition of the blood in passing through the 

 kidneys Physiological anatomy of the urinary passages Mechanism of 

 the discharge of urine. 



THE striking peculiarities which the kidney presents in 

 its structure, as compared with the true glands, and the fact 

 of the voluntary discharge of its secretion at certain inter- 

 vals, would naturally lead to a closer study of the mechanism 

 of the production and discharge of the urine, than we have 

 given under the general head of mechanism of the formation 

 of the excretions. The composition of the urine, also, will 

 be found to be exceedingly complex, and its various ingre- 

 dients bear the closest relation to the processes of nutrition 

 and disassimilation ; all of which considerations render it of 

 the greatest importance to ascertain the precise mode of its 

 formation, and to study all the conditions by which this pro- 

 cess may be modified. In the present state of our knowl- 

 edge, we must certainly regard the excrementitious con- 

 stituents of the urine as formed essentially in the system at 

 large, and merely separated from the blood by the kidneys ; 

 and a consideration of these effete principles belongs to the 



