KIDNEY. 



is comparatively fmull : in the other cafe, the capacity of 

 the refervuir coiifiderably exceeds the fize of the glandular 

 organs. A part only of the bile pafTes into the gall-bladder, 

 the remainder flowing directly into the duodenum ; and this 

 fecretion fce'.ns not to be very aCli%e in the intervals of the 

 digellive proccfs. The kidnies, on the contrary, are always 

 aclive, and the whole of the fluid which they feparate 

 paffes into the urinary bladder. 



Two fmail bodies, placed near the kidnies, and called the 

 renal capfules, receive their veflels for the mod part from 

 the renal : we (hall therefore unite their defcription with 

 that of the kidnies. 



The kidnies are placed deeply in the lumbar regions, 

 at the fides of the vertebral column. They are ufualiy 

 two, a right and a left ; but the number is expofed to 

 occafional unimportant variations. Sometimes the two are 

 united by their upper or lower extremities, fo as to form 

 a crefcent, with the concavity upwards or downwards, 

 fomething like the figure of a horfe-(hoe, from which the 

 gland, in thefe cafes, is fonietimes named : or, there may 

 be an unulually large one on either fide, with two ureters, 

 and a deficiency of the oppofite gland : or, a fmall fuper- 

 numerary kidney on the front of the vertebral column. 

 Other deviations from the accuftomed ftrudlure have been 

 regiftered by anatomiils ; but all thefe varieties are unim- 

 portant in phyfiology. 



They are furruunded by a large quantity of fat, of a 

 peculiar fl;rufture and properties. This fubfi:ance is con- 

 tained in a loofe and eafily lacerable ctlhilar texture, which 

 connefts it to the kidney ; it forms a complete cafe, ifolat- 

 ing thefe organs from the furrounding parts. Its quantity 

 varies remarkably in different fubjefts, being fo abundant 

 as to hide the organs where the individual is very fat, and 

 very fparing in the oppofite llate. This fat is remarkable 

 for j;ro» ing hard when it is cold, particularly in the rumi- 

 nating herbivorous animals, where it is diftinguifhed by the 

 name of fuel. 



On account of the different bulk of the liver and fpleen, 

 the two organs, which are placed immediately above the 

 kidnies, the latter are fomewhat differently fituated on the 

 two fides of the body, the right being rather lower than 

 the left : the difference in this refpect may amount to an 

 incii, but it is not conllant. They both he deeply buried 

 behind the abdominal vilcera ; the right having above it 

 the renal capiule and the liver, and in front the colon and 

 coscum, the duodenum, and the other fmall intellme ; the left 

 being covered by the fpleen and pancreas, flomach, colon, 

 and fmall inteilinc. 



The figure is julUy compared to that of the kidney bean, 

 with the concavity placed inwards. It is elongated from 

 above downwards, convex in the greateft part of its cir- 

 cumference, and rather broadell at its upper end. The fize 

 varies confiderably, from four ounces in the adult to five, 

 fix, or even a pound : often one is confiderably larger than 

 the other. 



In order to defcribe more exaftly the external form and 

 the relations of the kidney, we divide it into two furfaces 

 and a circu r.terence. 'i'he antenor fuitace is flightly convex : 

 fometimes completely covered by the peritoneum, with the 

 interfed'tion of a itratum of variable thicknefs of fat and 

 loofe cellular fubiVaace ; and fonietin.es in more or lefs im- 

 mediate contact with tlie correfponding part of the colon : 

 for in fome fubjects tlie membrane fimply paffes in front of 

 the inlellinc, and binds it to the kidney, while in others 

 there is a more or lefs loofe fold, called the lumbar mefo- 

 colon. From tlie right kidney the peritoneum rifcs to the 

 liver above, and even to the diaphragm ; below, it palfes 



to the colon and duodenum ; on the left fide it goes to the 

 colon and fpleen. Cellular fubflance, containing more or 

 lefs fat, always co'.:net~ts the front furface of the kidney 

 to the membrane ; fo that the gland is behind the cavity 

 formed by that membrane, and would not be enumerated 

 among the abdominal vifcera, if that epithet were con- 

 fined to the parts contained within the cavity of the mem- 

 brane. 



The poflerior furface is nearly plane, and reffs on a 

 thick layer of fat, which feparates it from the lower part 

 of the diaphragm, from the anterior layer of the aponeurofis 

 of the tranfverfus, where it covers the quadratus lumborum, 

 and from the pfoas magnus. 



Thus, there is placed behind the kidney the thick mafs 

 of foft parts, which extends from the pelvis to the chelt, 

 protecting the organ from all external injury, and rendering 

 it nearly inacceflible to the knife of the furgeon. It is 

 alfo fupported behind by the two or three laft ribs. In 

 its longitudinal diredlion it corrcfponds nearly to the two 

 lail dorfal, and the two neighbouring lumbar vertebrae. 



The circumference of the kidney prefents a thick and 

 rounded extremity above, covered by the concave bafis of 

 the renal capfule ; a thinner and more elongated end below, 

 approaching more or lefs nearly to the crilfa of the ilium : 

 a convex, Uiick, and rounded edge, turned outwards, and 

 correfponding to the mufcular parietes of the abdomen and 

 the diaphragm ; a deep excavation on the infide, called the 

 notch of the kidney. This notch has thick and rounded 

 edges, and contains fome fat. The divifions of the renal 

 artery occupy the upper and front part, thofe of the 

 vein are placed behind : the pelvis occupies the deepeft 

 portion, and tlie commencement of the ureter is feen below. 



The confiftence of the kidney is remarkably firm, ex- 

 ceeding, in this refped, all other glandular organs. Its 

 colour is reddifh, with a tinge of brown ; but the intenfity 

 varies according to the quantity of blood contained in the 

 veffels.' When an animal has died of hemorrhage, it is quite 

 pale. The ftruAure of the organ comprehends a peculiar 

 glandular tifTue, arteries, veins, lymphatics, nerves, excretory 

 tubes, and a peculiar membrane. 



The proper tiffue of the kidney is remarkable for its 

 firmnefs. It will be bell underltood by carrynijj a fc£lion 

 through the kidney, fo as to divide it into an anterior and 

 a pollerior half. VVe firall then be able to dillinguiih very 

 clearly two fubflances ; an exterior, which is called the 

 cortical or arterial, and an interior, named the tubular or 

 uriniferous. All kidnies are not equally well fuited for this 

 examination : in fome, without any alteration from difeafe, 

 the two fubltances are confided together. The contrail of 

 the two component parts is feen particularly cleariy after 

 minute injeftion. 



The feclion of the kidney prefents to us alfo, difpofed in 

 a ftill more deeply feated ilratum than the tubular part, a 

 feries of fmall bodies, called papilla or maimlU, which are 

 merely the apices of the fmall cones formed by the tubular 

 fubllance. Many anatomiils defcribe thefe as a third fub- 

 ilance, under the name of the mamillary. Lallly, we obferve 

 the infundibiilaor calyce.i, and the pelvis, befides the orifices 

 of divided veflels fcattered here and there. 



The cortical fubllance is fo named becaufe it covers tlie 

 exterior furface of the organ : it is about two lines in 

 thicknefs. Its colour is a pulilh red, inclining to yellow : 

 its confiilence is lefs firm than that of the tubular, and is 

 about the fame with that of the liver, fo that it maybe torn 

 eafily. It is fmoolh externally, and clofcly connccled to 

 the proper membrane of the kidney. Internally it is con- 

 tinuous with the tubular fubtlance, and it forms prolongs- 



