On ground such as I have referred to, I believe there is much practical value in the views based on the colloid theory relative to the formation of stone. It certainly offers a reasonable and demonstra ble explanation, founded on what appears to be a precisely analogous process, of the fact that stones are usually formed in the human body not by the aggregation of salts the elements of which are foreign to the system, but by that of those which it is the natural province of the kidneys to excrete in not necessarily excessive quantities.
The other process of concretion differs from the foregoing, as it is dependent upon inflammation, it being requisite for the formation of a triple-phosphate stone that the inorganic element composing it should first be precipitated by the decomposition or a rearrangement of the urine. When this has been accomplished, then the coalescence of ' the gritty particles may be brought about as in the preceding manner.
It is probable that under such circumstances as these, the crys talline nuclei of calculi are collected and deposited within the kidney and increase in size within the area of the cortex, or in the more dis tinctly tubular portion of the organ. Hence we have cortical or some fixed stones in contradistinction to these lying comparatively loosely in the renal pelvis.
The terms " gravel" and " stone" are generally used to indicate the concretions formed within the urinary apparatus. The former is applied to the smaller varieties, while the latter denote those stony masses which as a rule require some surgical procedure for their re moval. There is, however, no arbitrary limit between the one and the other. A retained gravel is, sooner or later, likely to attain the dimensions of a stone.
These concretions are met with at all periods of life, and they have even been discovered within the kidneys of new-born children. I
once saw a female infant, only a few months old, in whom a sharp hmmaturia was clue to the passage of uric acid crystals of sufficient size to be palpable to the touch. Under a diet composed of Con trexeville water, milk, and barley water in equal proportions the symptoms and the gravel entirely disappeared.
Physical stones vary much in size, shape, and numbers. Some stones are round like peas and are often present within the kidneys in considerable numbers, though their form ena bles them to escape along the ureters into the bladder with tolerable ease. Other stones are built up evidently by an aggregation of crys tals. These, as for instance in the case of oxalate of lime, though they may not be much larger than those just referred to, are exceed ingly irregular in outline and are liable to scratch and pain the parts over which they are passed or along which, as in the case of the ure ters, they are extruded. Some renal stones are of considerable size, weighing many ounces, and are branched in the form of the interior of the kidney. Such specimens, by their growth and pressure, apart from the inflammation they are liable to excite, eventually bring about the disorganization and destruction of the organ in which they are situated. A stone in the kidney is to all intents and purposes a foreign body, and must be looked upon as such.
One or both kidneys may be the habitat of a calculus, and when, as sometimes is the case, both ureters become in this way occluded, the condition of the patient may be looked upon as imminently fatal unless the cause of the obstruction can be removed either without or with a surgical operation. These instances will again be referred to.