The medical practitioner cannot be said to have entirely performed his duty by treating successfully a disease which, withstands in general the efforts of others, unless he also makes it known the means to which such success may be attributed. Was this idea more strongly impressed, than it appears to be on the minds of professional men, the page of medical history could not fail of having been enriched even beyond its present state. Many a valuable fact, I am persuaded, has gone down with its possessor to the grave, which, if communicated to the world, would at once have benefited the community, and rescued from oblivion the name of its observer. Nor is the communication of successful practice alone attended with advantage. The correct and impartial detail of those cases, which baffle our exertions, has also its utility; for, from the failure of the remedies employed, we receive a lesson which should be carefully remembered. We are taught thereby fairly to appreciate the value of the means recommended, and, from a perception of the insufficiency of our knowledge, are led to the extension of our inquiries. Induced by a belief that the history of the following case may be attended with beneficial consequences, I take the liberty to request its insertion, with remarks, in your valuable Journal. 

John Cronin, a countryman employed in the Ordnance Department at Spike Island, Cork harbour, applied to me for relief of what he considered mere debility, on the 14th November 1806. He was greatly emaciated, had a constant hectic flush, and his under eyelids were red and inflamed; his skin was dry and scurfy; he had continual and excessive thirst, and a ravenous craving for food. The pulse was 90 in the minute, and was somewhat hurried; his breathing, however, did not appear affected. His belly was natural, but the secretion of urine, which was the oniy circumstance he omitted in his account of his complaint, I discovered to be very considerable. 

On the 16th he was admitted into the Ordnance Hospital at Spike Island ; on that day he made 16 pints, by measurement, of a clear and almost colourless water, without odour, and perfectly sweet to the taste. On examination into the previous history of the disease, I learned, that he had always been very temperate, and extremely healthy, till about thirteen months before this period, when, after being much heated, he drank cold water, and lay a short time on the grass. This imprudence was very soon followed by a copious discharge of urine, by no means, however, so great as at the time he made application to me for relief. The increase of the urinary discharge was succeeded by the other symptoms before enumerated, which, by degrees, arrived at the height already described. One circumstance particularly deserving of notice, was the tendency which milk at all times had to augment the flow of urine. 

He was ordered to be confined to a strict animal diet, consisting of one pound of boiled beef without bone, and two quarts of strong soup, without any vegetable ingredient, in the course of the day; he was also ordered to take a drachm of the pulv. cinchon. three times a day, each dose to be taken about an hour before he made use of solid food. On the 17th, the urine, though diminished little more than a pint, was somewhat less sweet to the taste, and emitted a more heavy odour, a circumstance which gave me some little hope of success. The bark was continued ; and as he complained of great thirst, and a very painful gnawing sensation of the stomach, whenever it was empty, his allowance of meat was doubled, and another quart of broth was added to his drink. 

On the 18th, the urine was surprisingly diminished, hardly exceeding seven pints. It had assumed, besides, a much deeper colour and, both in smell and taste, differed little from the natural state. His thirst was considerably diminished, but his appetite still continued voracious. Ordered to go on as before. 

On the 19th, he made but five pints of urine, which bore all the characteristic marks of a natural secretion ; the thirst was nearly gone ; the appetite, though less, was still, considerable. He was directed to proceed.

 On the 20th, his urine did not exceed four pints; the appetite was much diminished, and the thirst entirely gone. As he wished to go home to his family, who resided a few miles distant, and as no provision is made by the Board of Ordnance, excepting for those actually hurt upon their works, (and even their patients of the civil branch cannot be detained against their consent), he was dismissed from hospital. Before his departure, I explained to him very particularly the nature of the disease, from which he had so fair a prospect of being perfectly relieved, by a steady perseverance in the plan I had adopted. I also pointed out to him the certain fatality of the complaint, unless treated after this manner; and expressed my decided opinion, that his disorder would return should he deviate, in the smallest degree, from my instructions. He seemed perfectly aware of his own danger; and, in order to enable him to follow my advice, I gave him a letter to a friend of mine, on whose estate he resided, who kindly and humanely supplied him with the necessary food, and who, being interested by the peculiarity of the case, and method of treatment, in a great measure, inspected the matter himself. 

My patient called upon me once a week for bark, and at the end of the sixth week, (December 25th), he was allowed half a pound of bread at dinner. From that day he continued to use vegetable food without restraint, and has experienced no return of the disease. He has since regained his strength, and his former healthy appearance. 

Remarks. The success of this case must be attributed entirely to the use of the animal diet, as bark, when given without prohibition from vegetable food, has but little effect in the cure of this truly formidable disease. The cinchona was prescribed with a view to its invigorating principle, which enables the chylopoetic viscera to perform their functions. This I think it necessary to mention, lest it should be supposed to be my wish to recommend the use of that medicine with any other view, but as an auxiliary to the only plan which has yet been generally adopted with success. As an auxiliary, I must, however, consider it preferable to anyother, for the reason already assigned. At the same time, I will not deny, that other remedies may also have their uses in the same way. The use of septics, which Dr Rollo strongly recommends, in his valuable publication on this subject, was first tried by Dr Francis Home, in two cases, which occurred at the Royal Infirmary of Edinburgh. Dr H. was induced, he says, to try the use of septics, in order to promote the animal process, as the urine appeared too little animalized ; " and," he observes, " it is the first time that I, or perhaps any other, ever pursued that idea." It is indeed not a little singular, that Dr H. did not follow up this idea, or that of reducing the quantity of urine by incrassants. By the latter plan, the urine of one of his patients was diminished from 12 to nine pints in the 24 hours; and it should be remarked, that this patient got 30 oysters in the course of the day. This, however, was reserved for the sagacity of the learned Dr Rollo, to whom, whatever may be the theory entertained by that enlightened physician, the medical world is certainly indebted for the suggestion of the plan of animal diet alone, and which cannot fail of transmitting his name with honour to posterity. The rapid change in the state of the urinary discharge from the use of animal food, is a circumstance, which, though noticed by Dr R., must excite considerable surprise. It was one, which, whatever hopes I might have entertained from a steady perseverance in the method of treatment adopted, I was by no means prepared to expect. Our astonishment, however, must, no doubt, suffer some diminution, from a consideration of Dr R.'s experiments, which very clearly demonstrate, that the urinary, or rather saccharine, secretion in diabetes, depends on the imperfect animalization of the blood, and that such imperfect animalization is the consequence of defective assimilation of the aliment. This is very clearly deducible from those experiments, though Dr R., as I apprehend, considers the saccharine secretion as formed in the stomach. No dissection, as far as I know, has yet discovered the presence of a saccharine matter in the stomach, nor is it easy to conceive, that, if that viscus did secrete that matter, it could pass from the stomach unchanged to the bladder, unless we also acknowledge the existence of the vasa brevia, a, position denied by the most celebrated anatomists. Dr R. mentions, (in the case of Captain Meredith), that the patient was bled, and the blood was kept for several months, without undergoing any putrefactive process ; while a portion of healthy blood, taken at the same time, and placed in the same room, exhibited evident marks of great putrefaction in four days, and was obliged to be thrown away on the seventh. This circumstance leads me to adopt, in preference, the theory of the saccharine secretion being performed by the kidneys, and which is well expressed by Dr Baillie. ( From the state of the kidneys," says this celebrated morbid anatomist, " upon examination, it seemed to me probable, that diabetes depends, in a considerable degree, Upon a deranged action of the secretory structure of the kidneys, by which the blood there is disposed to new combinations. The effect of these combinations is the production of a saccharine matter. I think it probable, at the same time, that the chyle may be so imperfectly formed, as to make the blood be more readily changed into a saccharine substance by the action of the Icidneys The cause of the imperfect animalization of the blood will necessarily appear to be imperfect digestion, or defective assimilation of the aliment. This by some has been supposed to depend on disease, either in the structure or functions of the liver. This was the opinion of Actuarius among the ancient, and of Mead amongst the modern medical writers ; but later observations have not confirmed this idea. Dr Home examined very Carefully one of the cases before mentioned, which terminated fatally, and reports the liver "natural." Dr Baillie's history of the dissection of a case, which occurred to him, at St George's Hospital, London, is very satisfactory : He remarks, "the liver, at the same time, I examined with care, because it has been thought by some to be the chief source of disease in diabetic patients; but it was perfectly sound." Even allowing the liver to be sometimes engaged, it is a circumstance which, as Cullen observes, does not often take place, and therefore the disease must acknowledge a different cause. The mesenteric and pancreatic glands have likewise been said, in some instances, to have been enlarged and diseased ; and the latter, especially, have been found, in two cases, to have been much altered in their structure, by an eminent professional friend of mine, in Cork, whose name I am not at liberty to mention ; but this is only casual, and cannot be set down as the general cause of diabetes ; yet one idea strikes me, from a consideration of the histories of the chylopoetic viscera being sometimes found diseased in this complaint, and which I submit with much diffidence: It is, that where diabetes resists the plan of animal diet, it may be fair to conclude, that diseased structure may be the cause, and thence, that a mercurial course might be, at the same time, attended with advantage. The utility of this plan will perhaps be more apparent from a consideration of the declaration of the very accurate and learned Dr Willan, in his reports on the diseases in London, " that this disease has been relieved, and the saccharine quality of the urine removed by animal diet, and the general plan recommended in Dr Rollo's treatise on this subject; but I never yet," he continues, " met with a confirmed case, wherein there was not some considerable disorder of the constitution, or a defect in some organ essential to life I do not see that any advantage is to be expected from local applications to the region of the kidneys : That the affection of those organs is but secondary, or, in other words, is dependant on the defective assimilation of the aliment, and the consequent imperfect animalization of the blood, will hardly be denied ; and the admission of this fact is necessarily followed by that of another, that the cure does not lie in any medicine or application, acting directly on the urinary organs, but in altering and correcting depraved digestion. This is most effectually done by the administration of those remedies which impart tone to the organs concerned, and by affording that kind of aliment onlyy whose direct tendency is to promote the animal process. I shall conclude this corrununication, by adverting to the place which this disease should have in systems of nosology. Dr Cullen has placed it under the order of spasmi. This improper arrangement has been wisely accounted for by Dr Willan, when he says, " most of the plans of nosology are exceptionable, as being founded on hypothetical principles, rather than a strict analogy between the diseases put in the same order if we attentively consider the circumstances attendant on diabetes, the emaciation, debility, oedematous swellings of the legs and feet, and, in some cases, (particularly towards the close of the disease), the quick pulse, and hectic flush, we shall be inclined to take the disease from the order in which Cullen has placed it, and rank it under the class of cachexiay and amongst the marcores. The tabes sudatoria resembles much, in its nature, diabetes; the former is attended with a diseased state of the primse viae, and cutaneous vessels, the latter with a diseased state of the primae viae and kidneys : In the former, the skin is evidently relaxed, and the histories of the dissections of diabetic patients shew a similar laxity and softness of the kidneys. The perspiratory discharge in the former, when collected on a sponge, speedily acquires a sour odour; the urine in diabetes soon undergoes the same change. To these may be added, that in the tabes sudatoria the urine is very scanty, while in diabetes the perspiratory discharge is, in a great measure, suppressed. The other symptoms are nearly the same; emaciation, debility, and hectic, equally mark both diseases. The analogy then, which subsists between diabetes and diseases usually ranked under the head of cachexia;, would, as before mentioned, strongly incline me to place it in that order. 

Cove, Cork.