OF THE reticule ORGANS.
The urine is secreted in two large glands, called the kidnies. These are situated behind the peritoneum, in that part of the abdomen termed the lumbar region, where they are surrounded by a quantity of loose cellular and aclipous substance. Their form resembles pretty exactly that of the kidney bean. There seems to be *small part as it were scoop ed out, opposite to tile bodies of the ver tebrz ; at this, which is called the notch of the kidney, the blood-vessels enter.
When we make a cut through the sub. stance of this organ, it is found to be made up of two substances, differing in appearance. The exterior is called the cortical orarterial part,the interior, which consists of several conical portions, is named the uriniferous. The latter remains perfectly white, if a kidney be injected.
Several very minute edtverging tubes are seen running through the uriniferous por tion, and terminating by open mouths on their conical points; these, which can he filled with minute injection from the ar teries, and the open mouths of which can be seen with the aid of a small magnify ing power, are thc excretory tubes, or tubuli uriniferi, of the kidney. The urini ferous portion of' the gland forms about fifteen conical projections, termed papil lm ; on each side of which the excretory tubes open in gteat numbers. The pa pmject into short membranous ca nals, called infundibula ; and these ter minate in a common receptacle, situated at the notch of the kidney, ind known by the name of the pelvis. From this, a ca nal about equal in size to a writing quill, the ureter, conveys the secreted fluid into the bladder.
The bladder is a membranous and mus cular reservoir, receiving the urine as it is found in the kidnies, retaining it until it has accumulated in some quantity, and then expelling it throait a canal called the urethra.
The internal surface of the bladder is formed by a smooth membrane, constant ly covered with a mucous secretion, which defends it from the irritating effects of the contained fluid. It has a muscular coat, sometinies described as a mesele, under the name of detrusor iirinze ; and that part of the fibres, which is situated round the opening of the urethra, is called the sphincter vesicx, as it keeps The aperture constantly closed, until we make an effort for the expulsion of' the contained fluid. The ureters open into the lower part of the bladder ; and open in such a manner, that, although the urine flows readily from them into the receptacle, none can return. They pass between the muscular and in ternal ,tunics, before they penetrate the latter.
The bladder is situated just behind the ossa pubis ; and is partly covered by the peritoneum. The urethra proceeds from its lower and anterior surface, and this part is called the neck of the bladder ; it then goes under the arch of the pubis. It forms in the female a canal about an inch and a half, or two inches long, which opens in the cavity left between the labia pudendi. In the male it is about nine in ches in length, and runs along the under part of the penis to the ektremity of that organ, where it opens.