Читать книгу Pharmacologia - John Ayrton Paris - Страница 58

Substances which, by direct application to the pituitary membrane, occasion a discharge from the nostrils either of a mucous or serous fluid. This class contains several different species, whose operation varies in intensity, as well as in duration.

Errhines have been regarded as useful in consequence of the evacuation they occasion, but in this respect their value has been greatly over-rated; it has been stated, that they diminish the quantity of fluid circulating in the neighbouring vessels, and even extend their influence to all the branches of the external carotid; and Dr. Cullen says that he has, apparently from this operation, known head-ache, pain of the ear, and some cases of ophthalmia, cured or relieved by the use of Errhines. There can be no doubt that local stimulants of this kind will frequently remove pain from the head and neighbouring parts, but not merely by occasioning vascular depletion, as Dr. Cullen supposed, but by a stimulant operation conveyed through the medium of nervous communication, or contiguous sympathy.

Dr. Cullen has moreover supposed, that these substances may be useful in preventing apoplexy or palsy. Morgagni^[171] however relates a case in which sneezing induced a fatal attack of this disease; and Van Swieten^[172] has satisfactorily shewn, that continued paroxysms of sneezing tend to load the vessels of the head with blood; for the violent contraction of the chest impedes, for a time, the passage of the blood through the lungs, and therefore obstructs the return of the venous blood from the brain, the vessels of which are in consequence greatly distended; the face therefore reddens and becomes turgid, the eyes are suffused with water, and appear full and distended. Its occasional dangerous violence is said to have given origin to the benediction so universally bestowed on those who sneeze.^[173]

It has been a subject of popular inquiry, how far the habitual use of Snuff may prove beneficial or injurious; and whether the habit, when once fully established, can be discontinued with impunity? It may be remarked that Snuff, by habitual use, soon ceases to produce the effect of an Errhine, for which reason its discontinuance cannot, generally, be regarded as likely to be attended with any danger; in those cases, however, in which the discharge is perpetuated, a contrary judgment should be pronounced, for all artificial discharges become constitutional by long continuance, and can therefore be seldom checked with impunity. Dr. Cullen states, from experience, that “whenever the nasal discharge has been considerable, the laying aside the custom of taking snuff has been productive of evil.”