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another place,* "the plague a second time attacked the Athenians, having, indeed, never entirely left them, though there had been some abatement of it. It lasted, the second time, not less than a year, the former attack having lasted two; so that nothing reduced the power of the Athenians more than this, for not less than four thousand four hundred heavyarmed in the ranks, died of it; and three hundred of the equestrian order, with a number of the multitude that was never ascertained. It was at this time also, that the numerous earthquakes happened at Athens, Eubea, and Boeotia, particularly at Orchomenos in the last-named country."

One circumstance mentioned in the foregoing passages from Thucydides, is worthy of particular notice, his direct allusion to the spread of this disease by infection, a subject rarely if ever referred to by the medical authorities of antiquity, and upon which I shall again have occasion to, speak in connection with Pliny's account of the Mentagra of the Romans.

Before closing our notice of medicine among the early Grecians, having already ventured beyond the strictly professional authorities, it is but proper to give some attention to an author whose writings, more than those of most other men, have been instrumental in exciting to discussion and inquiry in every branch of science. I allude to Aristotle. I need not in this connection refer to his influence as a teacher of philosophy. In this department he

* III. 87..

divided with Plato the admiration of the ancient world, and throughout the middle ages was held in supreme authority among the schoolmen. I refer to him here simply as a contributor to our knowledge of animated nature, to anatomy, and physiology, to the history of the lower animals, and of many of their diseases.

The work of Aristotle, entitled "De Animalibus Historiæ," is divided into nine books. In book first he gives the configuration of every organ and part of the human body, accessible to the sight without the aid of dissection; next, acknowledging his utter ignorance of the internal structure of the body, he proceeds to describe that of such lower animals as are thought to hear the greatest resemblance to the human race. In book second he, gives the organization of the various classes of animals supplied with blood, meaning such as have red blood. In book third he gives a treatise on what would now be called general anatomy, or the anatomy of the simple tissues and structures: the blood-vessels, and the heart; the nervous, and what we would call the tendinous, and some of the membranous tissues and organs; the firmer fibrous tissues; the bones, the cartilages, the tegumentary envelopes and their modifications in different classes of animals; the substance of the brain and its envelopes; the envelopes of the bones; the muscular tissue; the fat; the blood; the medulla of bones; the

Aristotelis de Animalibus Historiæ libri x. Lipsiæ, 1811, 4 vols. 8vo., of which the last book is spurious. :

milk, and seminal fluid. In book fourth he proceeds to describe with equal care the organization of the different classes of animals without blood, or as we would say, having only white blood. Books fifth and sixth treat of the reproductive functions of the lower animals, from the simplest upwards; book seventh, of the corresponding functions in the human race; and the two remaining books, of the habits, localities, instincts, and propensities of the lower animals; several chapters of the eighth book being devoted to their diseases.

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His division of the parts of animals into simple and compound, was adopted by most of the later writers on anatomy, and particularly by Galen. He denies the assumption of Alcmeon, that goats are able to respire through their ears. He describes the two envelopes of the brain; the firmer investing the inner surface of the skull; the more delicate or venous membrane resembling a skin, surrounding the brain itself; which, he says, is without blood, and consists of two parts, the cerebrum and cerebellum. He alludes also to the lateral ventricles. He gives a sufficiently close and accurate description of the respiratory organs, and their connection with the heart. It is not certain, says he, when air has traversed the arteria aspera whether it passes directly to the heart by the lungs, in all animals; though he held such to be the fact in most of them. Of all the organs the heart alone holds blood within itself; for the blood of the lungs is not proper to them, but is contained within the vessels in communication with the 'heart.

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The blood in the middle sinus of the heart is the most attenuated.

He refers to the erroneous opinions of earlier writers, particularly to those of Syennesis of Cyprus, Diogenes Apolloniata, and Polybius, in regard to the origin and distribution of the blood-vessels; and after alluding to the difficulty of the investigation, proceeds to give his own account of them. These vessels, he declares, have not their origin in the head or brain; but are derived directly from the heart. Here the nerves also receive their origin. There are, he adds, two veins within the chest near the spine, the larger of which lies in front of the other, and more towards the right side. The smaller of the two is of a nervous structure when seen in the dead subject, and is called the aorta. Both of these vessels have their origin in the heart; through whatever viscera they pass, their course is continuous and uninterrupted. The heart constitutes, as it were, a part of them; particularly its anterior portion, where it is connected with veins passing both upwards and downwards; the heart itself resting in the midst. He attempts to show a connection between the branches of the vena-magna after passing through the diaphragm to the liver, with other veins passing upward towards the right axilla and arm; adding that the physicians, by drawing blood from the vessels of this arm, are enabled to cure certain diseases of the liver. A similar connection he elsewhere traces between the vessels of the spleen and those of the left arm.

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The blood is thicker and darker in the lower,

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than in the upper parts of the body. In the veins of all animals it is observed to palpitate. It is the only one of all the humors which is always present so long as life endures. It is supplied from the blandest fluids of the body, and formed within the heart. Deprived of it to a slight degree, the animal faints; to a greater extent, the animal dies. It changes in quality with the periods of life; and if too thin, it leads to diseases. When vitiated it gives rise to hæmorrhoidal flux, to epistaxis, to piles; and to varices. Pus is the result of its putrefaction. The bones, deprived of their fibrous envelope, desiccate; the bladder and other membranous or nervous sacks and tissues, when cut, never heal.

Among quadrupeds the hog is subject to three diseases, all of which he describes, giving the symptoms and mode of treatment, namely, - angina, which extends from the throat to the lungs and other parts of the body; scrofula, affecting the head and contiguous parts; and a disease of the bowels, which is usually fatal. Dogs are also subject to three diseases, rabies, angina, and podagra; all of which are briefly described. Rabies renders the animal insane, and all others that are bitten: by him, excepting man; and is fatal to all that are affected with it. And thus he treats on the diseases of other animals, savage and domestic.

From the foregoing exposition it will be seen that in his acquaintance with anatomy, physiology, and, we may also add, general pathology, Aristotle was far in advance of his epoch, approaching more closely to the medical science of modern times than

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