It may be said that these opinions were similar to those of the Ovarians, who, as we have observed already, believed that every thing arose from the egg. Such were Aristotle, Empedocles, and other philosophers: “For the egg is the conception,” said the first of these great men, “and after the same manner the animal is created;” but there was a manifest difference in their systems. Harvey, Haller, De Graef, were amongst the most warm advocates of this doctrine, which indeed prevails to the present day, as it would be difficult to find organized beings that did not spring from an original germ.
It thus appears that, notwithstanding the absurd doctrines of generation being founded upon the existence of these animalcules, they clearly do exist. Modern microscopic experiments daily confirm the fact; not only in the generative secretion, but in the other fluids of the body: creatures of an inch to an inch and a quarter in length have been found to inhabit the mesenteric arteries of asses and horses. Mr. Hodgson found them in seven asses out of nine. They have also been found in the blood of female frogs, salamanders, and tadpoles. What wonders are perhaps in store for the microscopic observer and the physiologist! All living matter seems to be animated by particles, by atoms, equally possessed of life. Does the vitality of these constituent molecules hold any influence over our existence? Is their life necessary to the preservation of ours? Is any agency destructive to them injurious or destructive to us? In a former paper I have recorded recent observations, where animalcules of a peculiar description were found in the purulent secretion attending various affections. A morbid condition seems thus to produce a new series of animated beings, or this new series of living atoms perhaps have produced a morbid state. Many eruptive maladies are either caused by the presence of insects, or insects are subsequently developed in their pustules. Wichmann, and many other physicians, have maintained that the itch was produced by an insect of the genus acarus, or tick.
Latreille has given a minute description of this creature in his Genera crustaceorum et insectorum, and calls this offensive species the sarcoptes scabiei. Linnæus classed it among the aptera, and termed it the acarus scabiei. This insect is nearly round, with eight legs; the four fore-legs terminated with a small head, the hind ones with a silky filament. The Arabian Avenzoar had long since observed them, and it was from his writings that Mouffet was induced to pursue the inquiry. Redi, an Italian physician, was the first propagator of this doctrine in modern times, and published, in 1685, a paper of Cestoni of Leghorn, who had frequently observed mendicants and galley-slaves extracting these insects from the pustules of itch with the point of a pin, in the same manner as chigoes are extracted from their cyst in the West Indies.
It was this communication of Cestoni that led to a further and more minute investigation. Curiosity was every where excited, and the most learned and intelligent naturalists and physicians, amongst whom we find the illustrious names of Borelli, Etmuller, Mead, Pringle, Pallas, Bonani, Linnæus, Morgagni, strove with incessant diligence to ascertain this important fact, which certainly was likely to shed a new light on our pathological speculations. The existence of the acarus was established.
The most conclusive experiments on the subject were those of Galès, in 1812. The following is the account of them: “I placed under a microscope a watch-glass with a drop of distilled water, after having carefully ascertained that it did not contain any visible animalcules. I then extracted from an itch pustule a small portion of the virus, which I diluted in the water with the point of a lancet. I watched most attentively for upwards of ten minutes, without having been able to notice any animation. Two similar experiments were equally ineffectual. Disappointed in my expectations, I was about giving up the task, when an idea struck me of submitting the liquid of the first experiment to another trial. I had left it in the watch-glass, exposed to solar heat. I then was not a little surprised when I discovered a perfect insect struggling with its legs to extricate itself from the viscid fluid that confined it. Having succeeded in reaching a more limpid part of the liquor, its form was so distinct that Mr. Patrix, who was with me, was enabled to take an exact drawing of its configuration.”
This curious result naturally induced Galès to pursue his inquiries, and he discovered that this insect chiefly occupies the pustules that are filled with a thin serum, and avoids those that contain a thicker secretion. Hence the watery pimples in itch are invariably those that produce the most intolerable prurience.
The next important question was to decide whether this insect was the cause of the disgusting disorder. For this purpose Galès placed several of them on the back of his hand. He then covered the part with a small watch-glass, kept in place with a bandage. Three hours after he awoke, experiencing a sensation of itching on the part. The following morning three itch pustules were evident, and convinced him that he had succeeded in inoculating himself with the loathsome complaint. This fact he communicated to Olivier, Duméril, Latreille, and Richerand. Experiments in the hospital were immediately directed to be made, and all produced a similar result; affording a convincing proof that these insects could produce the affection, which they had merely been thought to have complicated.
Many writers, who, like Mason Good, had decided that “whenever these insects appear, they are not a cause but a consequence of the disease,” opposed and contradicted the statement of Galès, and the numerous practitioners who had procured and witnessed facts, which are never “stubborn things” to speculative minds. These writers maintained that whenever any organ was weakened, or in a morbid condition, it was apt to become a nidus for some insects or worms to burrow in. Hence the numerous varieties of invermination in debility of the digestive organs. But it is needless to observe that their objections cannot stand against the imbodied evidence brought forward in proof of their error. Bosc, Huzard, Latreille, Duméril, and many other naturalists, subsequently found these acari in the eruptive diseases of many animals.
I repeat it, this subject is replete with interest; and microscopic experiments may some time or other throw a material light on the practice of medicine. Those substances that are known to destroy the insect that produces the itch, cure the malady. May not this analogy lead to singular results?