THE KIDNEYS SECRETION OF URINE. 495 



tend to remove pressure from the free surface of the vessels, and so to en- 

 courage the escape of their more fluid contents."- Here we see the essential 

 difference which exists between the vital agency concerned in the true Secivt- 

 iug process, and the physical power which occasions fluid exhalation or trausu- 

 dation. This difference is precisely the same as that which exists between 

 the vital act of selective absorption, and the jilnjxieal operation of endosniose 

 or imbibition. By Imbibition and Transudation, certain fluids may pass 

 through organic membranes, in the dead as well as iu the living body ; and 

 this passage depends merely upon the physical condition of the part, in re- 

 gard to the amount and the nature of the fluid it contains, and the permea- 

 bility of its tissues. There are two sets of lymphatics in the Kidneys, one of 

 which emerges with the bloodvessels at the hilus, whilst the other arises 

 amongst the fasciculi of the capsule. Little is known in regard to the nerves 

 except that they belong to the sympathetic system, are connected with gan- 

 glion-cells, and contain both sensory and vaso-motor fibres. 1 To chemical 

 investigation the tissue of the kidney yields Inosite, Tauriu, Leuciu, Tyro- 

 sin, Kreatin, Xanthin, Hypoxauthin, Cystin, and sometimes Urea and Uric 

 Acid. 



405. The Kidney is liable to undergo alterations of its normal structure, 

 from a perversion of its ordinary formative processes, which are of a nature 

 very analogous to those occurring in the Liver, though with differences 

 arising out of the specialties of its conformation. 2 Several different kinds, as 

 well as degrees, of such alteration, have been described (as it now appears) 

 under the general term " Bright's disease," which has been applied almost 

 indiscriminately to almost every kind of chronic disease of the structure of 

 the Kidney, whether produced by congestion, inflammation, or fatty degen- 

 eration, that is attended with the presence of Albumen in the Urine. It 

 must not be supposed, however, that any of these lesions are invariably coin- 

 cident with the presence of Albumen in the Urine: for it has been fully 

 proved, on the one hand, that albumen may present itself in this excretion, 

 without any alteration in the structure of the kidney ; whilst it has also been 

 shown, that various forms of Bright's disease may exist, even in an advanced 

 stage, without any albumen being detectable in the urine. 3 These variations 

 may probably be attributed to two classes of conditions, viz., the state of 

 the albumen in the blood itself, and the state of the capillary circulation in 

 the kidney. We have seen the weak form of albumen which is first taken 

 up by absorption from the alimentary canal, is distinguished by its prone- 

 ness to transudation ( 140); whilst, on the other hand, the strong albumen 

 of the egg, if injected into the systemic blood-current, or even if introduced 

 in large quantities into the stomach, 4 finds its way out again by the urine, as 

 a foreign substance ; an assimilating action being required, in the case of 

 each, to give it the normal character of blood-albumen. It is probably, in 

 part at least, to the want of such perfect assimilation of the newly absorbed 

 albumen, that we are to attribute the increase of albumen in the urine passed 

 soon after meals, by patients suffering under Bright's disease ; something, 



1 See Lionel Beale, Kidney Diseases, etc., 1869, p. 17; Tyson, American Journal 

 of Medical Sciences, 1869, p. 395; Lancet, vol. i, 1870, p. 57. 



2 For full accounts of the pathological conditions of the Kidneys and of the Urine 

 in "Bright's disease," the reader is referred to the recent works of Drs. Basham, 

 Johnson, Dickinson, and Beale. 



3 See Dr. Begbie in the Brit, and For. Med.-Chir. Kev., vol. xii, p. 46. 



4 See Hammond (Experimental Researches, Philadelphia, 1857, p. 31), who found 

 on restricting himself to a purely albuminous diet, that his urine first contained a 

 great excess of urea, and on the eighth day albumen made its appearance. Bernard 

 also observed its presence in his urine after eating six eggs fasting (Le9ons, 1859, vol. 

 ii, p. 138). 



