Camphor probably acts on the system at large exclusively through the blood. That it is absorbed is proved by its odour in the breath and perspiration, and, as some have asserted, in the urine, and by the result of an experiment of Tiedemann and Gmelin, who distinctly perceived the smell of camphor in the portal blood of a horse, to which the drug had been given.

From what has been stated above, it has been already inferred that 1 consider camphor as directly stimulant, both locally and generally, with very little comparative influence on the circulation, but a powerful action in large doses on the brain, and as indirectly sedative to all the functions, including of course that of the heart, through the over-stimulation or congestion of the nervous centres.

3. Camphor Therapeutic Application

Camphor was probably unknown to the ancient Greek and Roman physicians, and was introduced into Europe by the Arabians. In small doses of from one to three grains, repeated at short intervals if required, it often answers an admirable purpose as a nervous stimulant, relieving slight pains, vague uneasiness, nervous headaches, muscular twitchings, restlessness, jactitation, etc., and often enabling the patient to sleep by removing the causes which keep him awake. It is much used for this purpose in various diseases, generally in the state of camphor water, or combined with opium in the officinal camphorated tincture of opium, or paregoric.

In a full dose, calculated to act as a cerebral stimulant, it may be employed to stimulate the brain in a depressed state of its functions, to relieve pain, and to allay spasm and other nervous disorder. It probably produces the two latter effects by rendering the cerebral centres, through its congestive influence upon them, insensible to the impressions sent from the affected part, and incapable of transmitting influence to the muscular or other dependent function.

The following are the special diseases in which it has been most employed; but, whatever may be the name of the affection in which the indications above mentioned may be presented, it may be used to meet them, provided no contraindication exist.

Idiopathic Fevers. Whenever, in any one of these complaints, whatever may be the particular character of the fever, there may be general uneasiness, restlessness, jactitation, tremors, twitchings or starlings of the muscles, slight delirium, wakefulness, etc., and these symptoms may be in no degree dependent on, or connected with active congestion or inflammation of the brain, camphor may be employed as a nervous stimulant, and will often be found to act most happily in relieving them. The most convenient form for using it, under these circumstances, is that of the camphor water of the U. S. Pharmacopoeia, of which one or two tablespoonfuls may be given every hour or two, until the desired effect is produced. The symptoms referred to are peculiarly apt to occur in children, for whom, according to the age, the dose may vary from thirty minims to one or two fluidrachms, at the same intervals. Advantage will often accrue from combining or alternating it with compound spirit of ether (Hoffmann's anodyne), or with spirit of nitric ether (sweet spirit of nitre), under the same circumstances, and sometimes with one of the liquid preparations of opium, when that medicine may be simultaneously indicated.

In enteric and typhus fevers, and in the low typhoid state of febrile diseases generally, camphor is particularly indicated; and may sometimes be employed with benefit, not only for the purposes above mentioned, but also as a cerebral stimulant, in aid of wine-whey, carbonate of ammonia, etc., when the pulse is frequent and feeble, the tongue and skin dry, and the patient affected with low muttering delirium. The supposed diaphoretic property of the medicine comes here in aid of its stimulant action on the brain, which is in a depressed condition under the sedative influence of the depraved blood, or directly of some absorbed poison.

Inflammation. Under the impression of its sedative powers, camphor has been recommended strongly in inflammatory diseases generally, and especially in acute rheumatism, in which it has been supposed to exercise peculiarly beneficial powers. Of course it may be used in these complaints when the nervous symptoms above referred to call for it; but it is not in this capacity that its employment is now alluded to. It is supposed, in these complaints, to exercise a directly sedative influence over the inflammatory excitement, at the same time favouring perspiration. I have no doubt that it may act beneficially, but not precisely in the manner supposed. Whatever sedative influence it may exert is, I believe, secondary, and dependent on a direct stimulation and consequent congestion of the cerebral centres; and the inference from this view is. that it should not be employed in acute cerebral inflammation, or active cerebral congestion; nor, indeed, in any other inflammation with a full strong pulse and sthenic state of system, until the vascular fulness and excitement have been subdued by depletory measures. In other words, I think that it acts upon the same principles precisely as opium in these cases, and, like it, should be associated with medicines calculated to give it a direction to the skin, and obviate any stimulation it may produce, such as tartar emetic, the neutral mixture, nitre, etc. It is probably the similarity and, at the same time, inferiority of its action to that of opium, that has led to its disuse in inflammations; and advantage might sometimes accrue, particularly in inflammatory rheumatism, from having recourse to it as a substitute for opium, when that medicine, from its peculiar properties, may act in some way disadvantageously. When on the subject of opium, I shall more fully discuss its mode of operation in inflammations; and what may be said there will apply in considerable degree to camphor. With a view to its antiphlogistic effects, it must be used in full doses.

Painful Affections. Camphor has been occasionally used as an anodyne in neuralgia, but is much less efficient than several other medicines belonging to the class. In nervous headaches it may be useful, when they depend on cerebral depression; and, in slight cases, when the headache is merely an expression of some trivial nervous disorder, a small dose of camphor, with a little opium, as in the common paregoric elixir, will often operate happily. It is, however, in dysmenorrhoea that camphor has been most used merely as an anodyne. To fulfil this indication it must be given in the largest doses.

Spasmodic and other Nervous Disorders. In the more violent of the painful spasms, the anodyne and relaxing powers of camphor, in any ordinary dose, are quite inadequate to the results desired. It is of little use, therefore, in spasm of the stomach, ureters, or bile-ducts, in the severe forms of colic, in tetanus, etc.; yet it has been employed, with supposed advantage, in the violent cramps attendant upon poisoning by strychnia; and, in conjunction with opium, is occasionally used in epidemic cholera, and, in small doses, in the diarrhoea or cholerine preliminary to that disease. In the convulsive affections produced through the cerebral centres, it has sometimes been employed with great asserted benefit, particularly in puerperal convulsions; but, having no personal experience of it in this affection, I do not feel at liberty to recommend it. It has been used also in epilepsy, chorea, and hysterical convulsions with occasional advantage; but cannot be depended on for more than temporary relief, and often fails to produce that. In pertussis, and other instances of spasmodic cough, it may be given as an adjuvant to more efficient medicines; but is little used. In the cough attendant upon in-flammatory affections of the chest, in their advanced stages and chronic forms, it may sometimes be usefully associated with expectorants, when opium may be contraindicated, or in connection with that narcotic. In the form of camphorated tincture of opium, it very often enters into cough mixtures under the circumstances mentioned; but, in this form, should not be employed in the earlier stages. In the various slighter nervous disorders of hysteria, of the puerperal state, of hypochondriasis, of feeble paralytic cases. and of chronic debility in general, it may be used with occasional benefit, in small doses, as a nervous stimulant, either alone, or associated with other medicines.

It has been much used by some practitioners in insanity to produce sleep and quiet irritation; and may be considered as indicated in that complaint under similar circumstances with opium, to which, however, it is greatly inferior. It has been particularly recommended in melancholy. In occasional attacks of apparently causeless menial depression, it sometimes acts very happily.

From its stimulant influence on the nervous centres, it has been used in cases of amaurosis, of a purely functional character, with asserted success; but it has, under these circumstances, generally been prescribed with other medicines, such as valerian, arnica, etc.

It has been used in delirium tremens to aid in procuring sleep, as well as in quieting the varied nervous disorders of that affection; but, if used at all, it should be merely as an adjuvant of opium, or in conjunction with other narcotics when opium cannot be used.

One of the applications of camphor about which there has been the greatest difference of opinion, is to the alleviation of irritations of the urino-genital apparatus. The testimony, however, in favour of its occasional efficiency in morbid sexual excitement is too strong to be rejected. Sometimes in small, and sometimes in large doses, it has been given, with at least temporary advantage, in cases of nymphomania, priapism, and uncontrollable venereal propensities exhibited in other forms. Alone, or associated with lactucarium or lupulin, it may always be given in such affections with hope of benefit.

Many employ it habitually to prevent or relieve strangury from Spanish Hies used for blistering. For this purpose it is sprinkled on the surface of the plaster before application, and is given internally to relieve the affection when produced. I have never, however, found any very satisfactory influence from it, in the doses in which I have been willing to employ it; but have no doubt that, in large doses, whether by the mouth or rectum, it would sometimes have the desired effect; but the relief obtained, under such circumstances, by an anodyne enema of laudanum is so prompt and certain, that I have seldom thought it worth while to resort to less efficient means.

Camphor has also been employed in the retrocession of cutaneous eruptions, in order to relieve internal irritation by its calming influence, and to favour the return of the eruption by its diaphoretic action.