116 



ful ; it does not so intimately affect the fluid subjected to it. It does not 

 change the heterogeneous qualities of those that are mixed with it, and 

 allows them to pass in a pure state*. 



This multitude of elements in the composition of urine, had surely 

 been understood by the ancients, before it was demonstrated by modern 

 chemistry : ibrthey considered it as a sort of extract of animal substance, 

 as a real lixivium, carrying off all that is impure in the economy, and 

 gave it the name of lotium^ which indicates that destination. 



Finally, the secretion of urine is more uniformly carried on : it is con- 

 tinual, or at least, does not exhibit so prominently those alterations of ac- 

 tion and repose, so apparent in the work of the other secretory organs. 

 When, in a case of retention of urine, we introduce a catheter into the 

 urinary bladder, and leave it there, the urine keeps dropping continually, 

 and would wet the patient's bed, if the orifice of the catheter were not 

 kept closed. In the Memoirs of the Academy of Sciences for the year 

 1761, there is related a case of singular conformation of the urinary 

 bladder. This musculo-membranous viscus protruded through an open- 

 ing at the lower part of the linea alba, and was turned inside out, so as to 

 present externally, its mucuous membrane. This case afforded an oppor- 

 tunity of observing the continual flow of the urine through the orifices of 

 the ureters, and of ascertaining the different circumstances attending this 

 process, either with regard to the qualities of this fluid or to the quantity 

 which might be voided, in a certain space of time ; and in this respect, 

 there was a good deal of difference, according to the state of sleep and 

 waking, to the quantity, and to the diuretic qualities of the drink. 



The urine contained in the ureters is turbid and imperfect $ its consti- 

 tuent parts are not thoroughly blended together, as may be observed, if 

 made to flow, by compressing the kidneys in a dead body. It improves 

 by passing along those ducts, acquires the characteristic qualities of 

 ui'ne, oozes at the surface of the papillae, and flows into the membranous 

 c allies which embrace the rounded terminations of the tubuli uriniferi. 

 The uiJQt) O f the calices forms the pelvis, or the expanded portion of the 

 ureters, o, membranous ducts, along which the urine is incessantly flow- 

 ing into the 1^^^. The urine flows into the bladder by its own weight, 

 and especially \ v tne ac tion of the parietes of the ureters, which possess 



* This opinion is very r, fferent from that ent ertained by Dr. THOMSON. He conceives 

 that it is not merely the abs,., action o{ a quant i t y o f water and of salts accumulated in 

 the blood which the kidneys p ,, forn% bm that a chem i ca l change is produced by them, 

 either upon the whole blood, or t least upon some important part of it. In proof of 

 this additional function, he adduce. the w mat ; on o f nephrin and uric acid, as he sup- 

 poses, in the kidneys. These two ^stances," he says, are formed in the kidneys, 

 and as they are thrown out, after ben, t formed, without being applied to any useful 

 purpose, they are certainly not formed m v e k i dne y s for their own sake. Some part 

 of the blood then must be decomposed in tlK kidnev> an d anew substance, or substan- 

 ces, must be formed ; and the urea and uric ac^ must j-, e f orme d at the same time, in 

 consequence ot the combined action of the aflim: es w hicii produce the change on the 

 blood ; and being useless, they are thrown out togv tne r with a quantity of water and 

 stilts, which in all probability were useful in bringjn, about the changes which take 

 place in the arteries and in the kidneys, but which are no longer of any service after 

 these changes are brought about. Thorn. Vol. IV. p. 62. 



This reasoning rests entirely on the assumption that those substances are actually 

 formed in the kidneys ; it is quite as probable that they are produced in other parts of 

 the body, and are, with other substances, removed from the blood by the action of 

 those organs. See APPENDIX, Note P, for some experiments and further observa- 

 tions in support of the latter opinion. Copland. 



