There is no surface attainable from without, to which medicinal applications have not been made, with reference to a curative influence on the surface itself. The conjunctiva, the nasal duct, the nostrils and various cavities communicating with them, the mouth and fauces, the pharynx and oesophagus, the internal auditory meatus, the Eustachian tube, the urethra and bladder, the vagina and uterus, have all been the seats of such applications. Particular names have been given to certain medicines thus employed. Liquid applications to the eye are called collyria or eye-waters; substances applied to the nostrils, errhines and sternutatories; liquids to the fauces, gargarismala, collutorea, or gargles; solid bodies intended to be chewed, masticatories; and those applied to the urino-genital passages, if liquids, simply injections, if solids, and introduced into the vagina, pessaries.

Of all these surfaces, those of the nostrils and mouth are the only ones to which medicines are habitually applied in reference to any other than a local effect. In consequence of the strong sympathies of the nasal passages with the brain, errhines and sternutatories are not unfrequently employed to rouse the nervous centres, and sometimes also to agitate the respiratory organs by the act of sneezing. Both to the Schneiderian and buccal mucous membrane, medicines are occasionally applied with a view to their revulsive impression, and to the latter sometimes in order to affect the system, as for example by rubbing the medicine upon the gums. It must be confessed, however, that this latter method cannot be looked on as peculiarly efficient; and it is probable that, when any considerable effect has been experienced, it has been the result rather of the portion of the medicine swallowed, than of that absorbed from the mucous membrane of the mouth. There is reason, nevertheless, to believe that medicines are actually absorbed from this membrane, particularly from the surface of the tongue; and substances applied to this organ, and held there for some time, are asserted to have exercised the same remedial influence as when swallowed, without unpleasant effect upon the stomach.

Even to the serous membranes, applications are sometimes made with a view to some alterative effect on these tissues. Thus, injections are thrown into the tunica vaginalis for the cure of hydrocele; and attempts have been successfully made, in a few instances, to cure dropsy by stimulant liquids thrown into the cavities of the pleura and peritoneum; but this practice is too hazardous for general adoption.

Blood-vessels. Many medicines, when injected into the veins, produce the same effects as when taken into the stomach, but generally operate more powerfully. Hence it was long since proposed to administer medicines in this way; and the method has been frequently tried. In some instances it has appeared to do good; but the general experience of its results has by no means been such as to counterbalance its obvious disadvantages; and it is only under the most urgent circumstances, and in cases otherwise desperate, that it would, in my estimation, be justifiable.

When medicines are absorbed into the circulation, they frequently undergo preliminary changes, which probably better adapt them for admixture with the blood. Being taken up gradually, they enter the circulation in extremely minute quantities at one time, so that the whole blood becomes equably impregnated, and the least possible shock is produced either on the circulating fluid, the vessels, or the system. When injected into the veins, it is impossible to introduce them thus gradually and cautiously, and, if the attempt were made, the time consumed would greatly aggravate the danger of the operation. The blood, therefore, at the point of injection becomes too strongly impregnated, and must produce on the tissues more than the desired effect; while it is scarcely possible to calculate what injurious influence may be exercised on its own qualities or constitution. We are too little acquainted with the chemical and vital reactions which take place, under such circumstances, to be able to infer a priori what results would ensue; and experiments have not yet been sufficiently numerous and varied to supply this deficiency. The most violent effects have sometimes been produced by substances which, in other modes of application, are quite bland and innocuous. Besides, there are the dangers of injecting air into the veins along with the medicine, and of giving rise to phlebitis by injury of the vein.

Inoculation has recently been proposed as another and safer method of introducing medicines into the blood-vessels; but I cannot conceive of any advantage it possesses over the endermic method, while it is liable to the great disadvantage that the medicine, to produce any effect on the system, must enter the blood in a highly concentrated state, and thus endanger too strong a local impression. An account of Langenbeck's method of applying medicines by inoculation is contained in the British and Foreign Medico-chirurgical Review for January, 1857 (Am. ed., p. 203).

Attention has recently been called by Sir J. Y. Simpson, of Edinburgh, to the use of medicated pessaries, from which he has found advantage in the production of specific impressions on the uterus and vagina. The medicine is incorporated with some soft solid; and, as in the case of suppositories, cacao butter is admirably well adapted to the purpose. Opiates, astringents both vegetable and mineral, and various other medicines may be employed in this way. (Edin. Med. Journ., May, 1865, p. 1042).