SPLANCHNOLOGY, 201 
substance forms the superficial lamina of the gland, is about two lines 
thick, and sends long prolongations inwards between the membranous 
fasciculi. A microscopical examination shows the cortex to be composed 
of numerous arterial and venous ramifications, entangled with convoluted 
uriniferous tubes (tubes of Ferrein); an immense number of small granules 
may also be detected. These are the corpora or acini of Malpighi. A 
Malpighian corpus or corpuscle is a tuft of capillary arteries, arranged in 
loops, close pressed together, and inclosed in a slight dilatation of the 
urinary tube, which thus forms a capsule to it. A small artery called vas 
inferens pierces this capsule, and then divides into the branches which are 
coiled up to form this minute vascular ball, from the interior of which a 
small vein (vas efferens) proceeds, smaller than the artery, and piercing the 
capsule close to it, enters the venous plexus surrounding the convoluted 
uriniferous tubes, and from which the blood is ultimately conveyed out of 
the kidneys by the renal or emulgent vein. We have thus two distinct 
systems of capillary vessels, through both of which the blood passes in its 
course from the arteries to the veins. The first is an arterial capillary 
system, forming the Malpighian tufts, contained within the uriniferous 
tubes; the second is the venous plexus which surrounds these convoluted 
tubes. It has been supposed that the former serve to liberate water and 
the more simple elements of the blood, while the latter eliminate the more 
complex urea, uric acid, &c. 
The tubular substance is internal to the cortex, and consists of fine vessels 
arranged in about fifteen pyramids; the bases directed outwards, the apices 
towards the hilum. At and near the apex these vessels are straight, but, 
proceeding outwards, they communicate ; and, on entering the cortical sub- 
stance, become twisted and convoluted in the most complicated manner. 
The papille, or the mammillary processes, form the apices of the cones. 
Each is perforated by a number of fine holes, the orifices of the individual 
tubes, and through which the urine flows when these are compressed. The 
extremities of the papille are embraced by the calyces, membranous cups 
which unite with each other at the other end to form the ureter. ‘Those 
ealyces of each extremity, as well as those in the centre, unite into the three 
small tubes, the infundibula, which, after a short course, terminate in the 
pelvis, an oval flattened reservoir, which is continued into the ureter. 
2. THE URETER is the excretory duct of the kidney, and extends to the 
urinary bladder. Each ureter is about eighteen inches long, and of the 
thickness of a goose-quill. They enter the bladder by passing obliquely 
between its muscular and mucous coats. 
Attached to the upper extremity of each kidney is a small gland-lke 
body, termed renal capsule, or supra-renal body. They are well supplied 
with vessels, but do not appear to be especially connected with the kidneys. 
Their use is unknown, although it is probable that with the thymus and 
thyroid bodies they are concerned most especially in the economy of the 
foetus. } 
3. Tue BLADDER, vesica wrinaria, is the reservoir of the urine, which con- 
stantly trickles into it from the ureters. It lies behind the pubes, and rests 
Qn7 
