In the foetus and infant of a year old the bladder in figure more resembles that of a qua druped; when distended, it is pyriform, like a bottle or a flask reversed, the larger end, or the superior fundus being in the abdomen, and the smaller extremity tapering into the urethra. This is the only portion in the pelvis ; at this age its vertical axis greatly exceeds its other diameters, and even when empty the greater portion of it is in the abdomen. As the child increases in years and size, its pelvis expands, the bladder gradually descends into this region, and in the same proportion its lower fundus enlarges, so that at about six or seven years of age it presents a more oval form, both extremi ties being nearly equal, and very little of it rising above the pubis, unless when distended. From this period it continues to acquire gra dually the adult figure ; that is, its inferior fundus and body enlarge, while the superior re mains stationary ; hence it becomes shorter in its proportions, and broader below, so as to assume the triangular shape when empty, and the ovoid when distended. About two months before birth the bladder is very much elongated, its upper extremity being somewhat pointed, and ap proaching the umbilicus in the direction of the urachus. When distended, it presents some what the appearance of a cylinder contracted at each extremity. Soon after birth the upper fundus becomes rounder, and then it acquires the pyriform figure, which in the course of a few years undergoes the gradual alterations that have been already noticed.
The capacity of the bladder in the adult cannot be accurately ascertained, as it varies from a number of circumstances, such as age and sex, health and disease : thus irritation general or local, ischuria renalis, cholera, &c.; will cause it to contract, while retention of urine, paralysis, fever, &c., will allow it to enlarge. Custom or habit will also affect it, likewise the position of the body, pregnancy, the nature or peculiar quality of diet, the tem perament of the individual, the temperature of the atmosphere, the state of society, &c. In the same individual it will at one time contract so as to retain only a few drops, and at another it will dilate so as to contain one, two, and even three pints. Generally it is more capa cious in women, particularly in those who have borne children, than in men.
In children the bladder, although very dis tensible under certain circumstances, is usually less capacious in proportion than in the adult or old, probably because it is more muscular and irritable ; and hence, too, the more fre quent desire to contract and empty its contents.
When the bladder is moderately distended, anatomists and pathologists have been in the custom of dividing it into four regions for the purpose of more accurate description ; viz., the superior part or the upper fundus, the middle part or body, the inferior part or the lower fundus, and the cervix or neck. This arrange ment is not very correct, for it can only apply to this organ when distended ; the term su perior fundus also is obviously objectionable, and was probably derived from examining this viscus in other animals, or in the human foetus where the lower fundus does not exist ; neither can any exact distinction, or even an approxima tion to such, be made between these several compartments. A. more accurate knowledge of
this organ may be obtained by examining both internally and externally its several aspects, which are six in number, and which may be regarded as distinct regions ; viz., an anterior and posterior, two lateral, and a superior and inferior. We shall examine each of these ex ternally, and defer any remarks on their in ternal aspect until we come to speak of the lining membrane or the mucous coat of the bladder.
The anterior region, in consequence of the obliquity of the pelvis, looks also downwards. When the bladder is contracted, this region is behind and in contact (cellular tissue only in tervening) with the lower half or three fourths of the symphysis pubis, and with the pubic and triangular or interosseous ligaments; when dis tended, it rises above the bone, and is connected by an abundance of cellular and adipose tissue to the lower portion of the recti and transversi muscles ; and as no peritoneum is there inter posed, this part can be punctured with safety during life. At the lower border of this region is the neck of the bladder, the upper surface of which is firmly attached to the lower edge of the symphysis pubis by two horizontally placed fibrous cords, which are named the anterior ligaments of the bladder, and which will be more particularly noticed presently. Between and beneath these, some veins also run upon this surface of the bladder. The whole of this region is deprived of any peritoneal or serous covering.
The posterior region has an aspect upwards also; it is smooth and covered throughout with peritoneum. When the bladder is contracted, this small region in the male pelvis is in con tact with the fore-part of the rectum, or with such of the floating abdominal viscera as may chance to intervene ; in the female with the fore-part of the uterus. When this region is distended, it presents a broad smooth convex surface, which presses more against the rectum and supports the convolutions of the small in testines.
The lateral regions, when the bladder is contracted, are little more than margins or edges, and present nothing worthy of notice; but when distended, each becomes a broad surface, somewhat triangular, the base below and the apex above, the posterior portion, nearly the half, is covered by peritoneum, the anterior portion is connected by cellular tissue to the parietes of the pelvis : the obliterated umbilical artery ascends along its superior posterior por tion, and the vas deferens, which crosses to the inside of the latter, runs along this region in an oblique direction downwards and backwards, and marks the anterior limit of the peritoneum. From this region the broad lateral fold of this membrane extends to the iliac fossa, and at its inferior border is that reflection of the vesical fascia which is named the true lateral ligament of the bladder.