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sants. They would be eaten into the bone by ver-? min, were they not to dust themselves often, in or* der by this means to pet rid of their troublesome lodgers. Storks and pitygeons are also very subject to them. It is said that there is a bfrd in the Brazils, called Taputa, which consists of nothing but skin, and bone and vermin. Thefll insects do not six indisserently on all parts of the bird they adhere to. Some lodge under the skm, particularly about the neck, where the bird cannot easily get at them With his bill ; others on i the quills os their seathers; others on the wings kc. An attentive observer with little trouble may easily convince himself us these fccts.
Insects do not less insest quadrupeds than birds; The Gad-fly pierces the skin of cows, deer and hogs* and deposits us eggs; the larvæ afterwards nestle between the skin and the flesh. Some are found in the heads of various animals, but chiefly in those of the deer kind. To this some people have attributed the annual casting of their horns. They insinuate themselves also into the noses of disserent quadrupeds. Shepherds know but too well how fatal they are in this case to the sheep they attack. Some penetrate even to the intestines, and move there as if, in long galleries. Such are found in the intestines of horfes j but besides these, what vast numbers of insects attach themselves externally to quadrupeds? Some flies chiefly insest dogs, others horii s. Disserent species of pediculi adhere sirmly to the skins of asses, dogs, horses, deer, sheep, iisc.
Man the most noble of animals, is a world inhabited by multitudes of insects. The famous Borelliy an author who certainly is intitled to credit, affirms that he discovered in human blood animalcules of a sigure similar to that oi wbases, swimming in it, ai
in a red sen. Other writers, equally learned and curious j mention larvæ found in the human brain, which proved fatal to some, tho others were happily relieved from them. Jnsects likewise find their way into the human stomach, whence they are expelled by means of emetics. Our. intestines, are not more exempt from them than those of other animals, as I had occasion to mention above. Our whole body, so to speak, is like a storehouse which furnishes food to an infinite number of insects. Some lodge between the (kin and the flesti where they live at our expence. Young children who are not kept clean, are chiefly exposed to the attacks of vermin ; and sometimes it has become necessary to make incisions in ordtr to extract them from the nose, the eye brows, the ears, and the tongues of many persons. There are sometimes animalcules under the skin of the hand, which Creep along and make little elevations similar to those made in the earth by a mole. The Indians often have the leg and sole of the foot attacked by long worms which cannot be extracted without the greatest precaution. If they are broken, and the least part remain in the limb or in the foot, the life of the person becomes endangered. There is also in the Indies a small kind of ilea called nigtta (Pulex penetrans) which is likewise exceedingly troublesome. It burrows between the nail and the flesh of the toes, making them iwell to such a degree, that it is- necessary to make an opening in them. One would think that the hardness of the bones would secure them from the insults of these animalcules; and yet some are found living and feeding there. It is needless to mention those that iftselt the external parts of our bodies, they are too well known. I shall therefore stop for a moment to consider the wonderful discoveries made by Leewenhoeck in the semen of animals.
That illustrious observer of nature perceived with' his microscope an insinite number of small animals' swimming in the speimatic liquor. This discovery made him conjecture'that the strongest and most vigorous of these animalcules were arrested in the.' matrix, where ihey were nourished, and grew and became at last a persect fœtus. What confirmed him the more in his opinion was, that in opening a semale rabbit, immediately after its commerce with the male, he found in the matrix a vast number of these living animalcules. The observations he made on the semen cf different persons seemed to make the thing certain. In that of a boy, there was nothing seen but little black points without motion; while in that of a young man sully grown, there were myriads moving about with the greatest activity. In that of old men some indeed were found, but they were without strength or vigour and almost dead. Lastly in' people that were sterile, these animals were not discovered, or if they were discovered, they were dead.
But he carried his observations surther, and" thought he could distinguish the difserent sexes in these animalcules: whence he concluded that animals conceived males or semales according as the different sexes were detained in the matrix, where they were fostered, and received enlargement.
These animalcules are exceeding")' small, and Leewenhoeck says, that a drop like a grain of sand contained many thousands of them. He found them smaller thnn thole globules that give to blood its,red colour, and he thii:ks that the place occupied by a grain of iV.nd, might contain an hundred thousand. Their bodies are round, growing somewhat thick towards the head, and gradually diminishing towards the tail, which is sive or six times longer, and about •five and twenty times more slender than the rest o* the body; it is likewise transparent. They bend it a little, and move themselves like eels in water. There is a very great difference between the young of these animalcules, and those that are come to maturity. The first have the body more slender, the tail three times shorter, and less pbinted /than the latter. In the semen of a ram, those animalcules swam in a string one aster another, as sheep do in water.
Many learned men have made the fame observations after Leewenhoeck. In this number are Huygens, Andry, Valisnieri, Wolff and Tummig. Car.theuser (hewed these animalcules some years ago at Halle in his lectures on experimental philolophy to more than sixty persons. Hartsoeker examined, during a course of thirty years the semen of a vast number of quadrupeds and birds. He compares the spermatic animalcules of the first to the tadpoles frequent in stagnant waters, which have not yet got feet; those of birds' resemble small worms or a very slender thread. These observations made him suppose that there were only two kinds of spermatic animalcules to wit, those of quadrupeds, and those of birds. He did not deny that there might be diversities according to the different species, especially between those of man and quadrupeds; but he said ihat these were jiot discernible on account of their minuteness and the velocity of their motions.
The defenders of this doctrine disagree when they come to explain how these animalcules contribute to the generation of the particular species of animal which has produced them. Some with Leewenhoeck believe that in the intercourse of viviparous animals, .one or more of these animalcules attach themselves, to the matrix, that others serve for their food, and
L 2 that at last they become a persect fœtus. They add that the ova in the svarium, only produce the secretion of certain fluids. In oviparous animals the egg answers the end of the matrix, and to it the animalcule attaches itself. It penetrates into the middle of the yolk where it gradually grows to its persection, Other authors dissent from this system, and maintain that, in copulation, one or more of these animalcules get up into the ovarium by the Fallopian tubes, and there penetrate into an egg, at that time in a proper state to receive them, by means of an aperture surnished with a valve which prevents their retreat. In this egg it is nourished and grows. Lastly, some authors assirm that these animalcules have not yet the sigure of a fœtus, and that they receive it by a transformation similar to that of a caterpillar changing into a butterfly.
I shall not venture to decide on these various opinions, or to determine whether the animalcules are necessary to procure conception, whether they serve (mly to cause a voluptuous situation, or if they are destined to any other use; still less will I support the ppinion I have detailed. It appears to me too singular, and liable to too many difsiculties, as various authors have shewn. It is certain, however, that these spermatic animalcules are worms of a particular kind, destined by the Creator to serve a particular purpose; but man'has not yet discovered that destination, so great is the impersection of human knowledge.
I hid almost forgot to mention that insects are found in the dry remains os plants and animals, ai} Well as in works of art- There are some dry legumes which have the shell as hard as that of a nut: but this hardness does not secure them from the piercing (ccih of some insects which reduce them to powder.