236 



REN. 



on the left side is covered by its corresponding 

 vein, and crosses the left psoas muscle. 



The renal arteries occasionally present some 

 anomalies as to their origin, mode of division, 

 or number. In some instances they arise 

 below the usual situation, from the aorta, 

 or even from the common iliac or hypogastric 

 artery. The two last-mentioned origins 

 are usually associated with an unusual po- 

 sition of the kidney, either in the iliac fossa 

 or in the cavity of the pelvis. Meckel* has 

 observed the two renal arteries arising by a 

 common trunk from the anterior part of the 

 aorta. 



The artery sometimes divides into two or 

 more branches immediately after its origin, in 

 which case one branch usually leaves the 

 others to enter one of the extremities of the 

 kidney. This irregularity forms an approach 

 to another, which consists in an increase in 

 the number of renal arteries, each kidney re- 

 ceiving two, three, or four branches having a 

 separate origin from the aorta. 



The emu/gent or renal vein commences in 

 the substance of the kidney by numerous mi- 

 nute branches, which unite into four or five 

 trunks, and these again unite to form a single 

 trunk, either in the fissure of the kidney, or at 

 a short distance from this point. The vein 

 passes almost transversely inwards to the vena 

 cava, the right vein being shorter than the left, 

 on account of the position of the vena cava to 

 the right of the spine ; the junction of the 

 right vein with the cava is also somewhat 

 higher than that of the left. The vena cava 

 presents a marked increase of size immediately 

 after receiving the renal veins. Each renal 

 vein is placed in front of the corresponding 

 artery ; the vein on the left side crosses over 

 the aorta. The renal veins receive some 

 small branches from the supra-renal capsule, 

 and from the reticular and adipose tissue sur- 

 rounding the kidney, and the left renal vein is 

 usually joined by the spermatic of the same 

 side. 



The lymphatics of the kidney are but little 

 known ; they are said to consist of a super- 

 ficial and a deep set, the latter being the most 

 abundant ; they pass from the fissure of the 

 kidney to the lymphatic glands which surround 

 the aorta and the vena cava. 



The nerves of the kidney are very numerous, 

 consisting of several small branches from the 

 lower and outer parts of the semilunar ganglion 

 and solar plexus, joined by the descending 

 branches of the small splanchnic nerve. The 

 renal plexus thus constituted accompanies the 

 artery into the fissure of the kidney. This 

 plexus sends numerous filaments to the sper- 

 matic plexus, and hence probably the sympa- 

 thetic connexion which exists between the 

 testicle and the kidney. 



Structure of the Kidney. In order to exa- 

 mine the general structure of the kidney, it is 

 necessary to make a longitudinal section from 

 the convex towards the concave border. On 

 examining the surface of such a section, it 



* Cruveilhier, Anatomic Descriptive. 



will be seen that the substance of the kidney 

 is composed of two portions, differing from 

 each other in their general appearance and 

 arrangement ; an external cortical, and an in- 

 ternal medullary portion. It will also be seen 

 that the entire organ is invested by a fibrous 

 capsule, which at the hilum becomes conti- 

 nuous with the pelvis of the kidney and with 

 the ureter. It appears desirable to examine 

 the general appearance and structure of these 

 several parts before proceeding to the consi- 

 deration of the minute anatomy of the kidney. 

 The cortical substance forms a layer about 

 two lines in thickness, which occupies the 

 surface of the kidney, and sends inwards pro- 

 longations, from one to three lines in thick- 

 ness, between the conical divisions of the 

 tubular substance. The colour of the cortical 

 substance is much influenced by the quantity 

 of blood which it contains. It is usually of a 

 lightish red colour, but in anaemic subjects it 

 very frequently presents a yellowish-white 

 appearance, this being the colour of the renal 

 tissue when deprived of blood. The cortical 

 substance is of a softish consistence, readily 

 tearing beneath the pressure of the finger, and 



Fig. 143. 



Section from the surface of the kidney to the apex 

 of one of the medullary cones. The plate is intro- 

 duced partly to show how accurate was Schumlan- 

 sky's knowledge of the general structure of the or- 

 gan, c, g, blood-vessels ; h, the artery terminating 

 in a cluster of Malpighian bodies ; q, s, t, straight 

 tubes, with their dichotomous divisions ; o, bundles 

 of these passing towards the surface and then be- 

 coming tortuous ; p, section of blood-vessels. (After 

 Schumlansky.) 



