URN

Urinary Calculi. —When the uric acid of the urine, ■which we have already stated to be one of its most insoluble contents, is secreted in any extraordinary proportion, it is pa ed in a solid state, generally in minute red crystals, or red sand; and these not unfrequently agglutinate, so as to form small calculi from the size of a pin's head upwards. These, pa ing with more or le pain from the kidney along the ureter into the bladder, produce what is termed a fit of gravel; and if one or more of them remain in the bladder, it then increases in size, and becoming too large to be pa ed with the urine, gives rise to symptoms of stone in the bladder. The increase of this nucleus will be more or le rapid, according to the state of the urine; but if the inordinate formation of uric acid continues, that substance will frequently be deposited upon it in succe ive layers, and it will sometimes thus attain a considerable size, and consist almost entirely of uric acid. But if the uric attack in the kidney is transient, the small uric calculus in the bladder usually becomes encrusted with a white deposit, composed of ammonio-magnesian phosphate, perhaps with more or le phosphate of lime, this mixture forming what has been termed the fusible calculus; and this gives rise to a second and frequent species of urinary calculus, namely, that in which a uric nucleus is enveloped in the phosphates. The natural tendency of the urine is to deposit the above-mentioned difficultly soluble phosphates upon any extraneous matter or nucleus which may chance to be in the bladder; but the rapidity with which it is deposited is very different in different individuals, and accordingly the increase in size of such a calculus is sometimes very slow, and sometimes extremely rapid; and as the violence of the symptoms generally depends (but not always) upon the size of the concretion, they will be subject to great consequent irregularity. It does occasionally happen that calculi are formed in the bladder independent of any morbid state of the urine itself, or of any uric nucleus sent down from the kidneys; but these cases are rare, and appear to depend upon the accumulation of sand and mucus in certain disordered states of the bladder, which is gradually indurated into a nucleus, and which then goes on to increase in the phosphates; so that, on cutting such a calculus through the centre, we do not, as in the majority of cases, observe a uric nucleus, but the whole concretion is white and more or le crystalline, and usually consists of little else than ammonio-magnesian phosphate. This outline of the formation of calculi includes by far the greater number of cases; but it occasionally happens that not only the nucleus, but the bulk of the stone, is made up of oxalate of lime, a substance which we have above alluded to as not belonging to healthy urine. When these calculi come direct from the kidney, they often are grey and smooth, and look almost like a hempseed; or, when more carefully examined, are found to be a congeries of little rounded particles; but when they have increased in the bladder, they are then generally rough and dark brown on the exterior, whence they have acquired the name of mulberry calculi. Another, and more rare substance, which forms gravel and calculi, is the cystic oxide; and in some very rare cases small concretions oi carbonate of lime have been voided, most probably originating in the prostate gland. Lastly, minute grains of silica are said to have been detected in the urine, and this substance has also been found in calculi; but it is rare, and in small quantity. In concluding this sketch of the -history of the urine and urinary calculi, we cannot too strong'ly insist upon the importance of attending to the early symptoms of the disease, and to its first announcement, which generally consists in habitual turbidne and deposits in the urine. All persons are subject to occasional appearances of this kmd; but when they are constant, they ought to be considered as alarming indications of further mischief. These, in their early stages, are almost always curable, either by diet, medicine, or both; but when once a stone has formed in the kidney or bladder, all hope of its removal, except by an operation (and even that not admi ible in the case of kidney calculi), is vain, nothing having been yet discovered to which the term solvent is properly applicable. The removal of the stone from the bladder is effected by operation in two ways: either by an incision into the bladder, and the removal of the <tone by a forceps, — this constitutes lithotomy; or by Uthotrity, in which certain instruments are introduced by the urethra, so as to grasp the stone, and enable the operator to reduce it to fragments sufficiently small to allow of being voided by the usual pa age. URN, in Mo es, is the hollow urn In which the spores or false seeds are lodged. UKN, ClNERAKYor [s. 1291]