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in the fifteenth volume of the Transactions of the Royal Society of Edinburgh, soon convinced me that it was the fungus described and figured by that accomplished physician, and that it was obtained from a phthisical cavity. This example of a vegetable growth in animal structure, tempts me to offer a few passing remarks, for which, if not directly practical, the interest of the subject will be accepted as an excuse. Professor Owen, in a paper on the “ Anatomy of the Flamingo,” presented the first proof that there are parasitic plants, as well as animals, occasionally attached to animal structures.* In other words, he demonstrated the existence of entophyta as well as of entozoa. In 1835, Signor Bassi, of Lodi, and Signor Bassano, of Milan, described the cryptogamic vegetation called Muscardine, which proves so destructive to the silkworm.f In 1840, M. Des Longchamps obtained a vegetable growth from the aërial cavities of the eider duck ; but, previously to this date, namely, in 1839, Schönlein and Rémak had demonstrated the mycodermata of tinea favosa, and Gruby had illustrated the same production. Füchs and Langenbeck, of Gottingen, expressed an opinion that such vegetations exist in every variety of cutaneous scrofula ; and Meynier, of Orleans, extended his speculations so far as to assume that warts are fungi of the order gymnospermia, lepra and psoriasis varieties of lichens and mosses, and pulmonary tubercles nothing but varieties of lycoperdon. Such ideas par

* Philos. Mag. 1833, vol. ii. p. 71, New Series.
+ Annales des Sciences Naturelles, vol. viii. p. 229.

I See an instructive paper on this subject by Mr. Busk, in the Microscopic Journal for 1841, p. 145.

take more of poetical fancy than of physiological deduction ; still the subject is well deserving of philosophical investigation. These growths do not afford any real countenance to the hypothesis of spontaneous generation. To me the notion of animal structure being converted into germinating plants, appears as absurd as a literal adoption of the ancient fable of Venus springing from the foam of the sea. There is, indeed, no apology for any such wild speculations. The spores of these entophytes may readily be imagined as floating abundantly in the atmosphere, ready to germinate in any nidus suitable for their sustenance, and having its vitality so impaired as to be incapable of resisting their development. There is something to arrest the attention of the contemplative mind in that exuberance of life which can thus find support even in the secretions of decaying structure. We can scarcely, without emotion, recognise in the dark corners of creation such organizations of beauty, reserved, as it were, to reward the inquiries of the zealous student of truth. Gazing on the minute yet beautiful forms thus brought to light, and reflecting on the wonderful arrangements for securing so great a variety of being, I cannot refrain from quoting the exclamation of Pliny, whose more limited opportunities filled him with delight by revelations of beauty even in the minute aspects of creation : “ In his tam parvis, atque quam nullis, quæ ratio, quanta vis, quam in extricabilis perfectio."* I must not permit myself to expatiate on such a theme; but you will suffer me to congratulate you on the abundant ap

* C. Plin. Sec. Hist. Nat. lib. xi. cap. 2. Lug. Bavar. 1669.

pliances now available for pursuing such investigations, and, above all, on your choice of a profession, which, amidst all its cares and weariness, has so much compensation in the way of incentive and reward, filling the mind with ever-new materials of interest, and raising it to high conceptions, and pious reverence towards the great Author of life.

LECTURE IV.

The pulse: general remarks on the causes of its modifications ;

average frequency in health; morning and evening pulseAcceleration in consumption—Effect of posture in health contrasted with effect in disease-Practical illustrations-Speculations regarding the cause.

THE painter, when he would represent a physician, generally depicts him with a finger on his patient's pulse, as though the principal indications of disordered health were thence to be derived; and it must be acknowledged that such an idea has received countenance from some eminent medical writers. If, however, this symptom has been over-rated, we must not on that account fall into the opposite extreme; and a little consideration will make it obvious that any important deviation from the healthy condition of the system can scarcely fail to modify the pulse. The terms of disparagement in which some authors, particularly Heberden, and Falconer, have spoken of the pulse, is, in some instances, attributable to a deficiency of tactus eruditus, and a consequent inability to appreciate any of its qualities, excepting those of quickness and slowness. An expression of Celsus, which appears to me to have been misapprehended, has also become so fixed in the medical mind, as imperceptibly to confirm an unreason

no

able distrust of this indication. But the remark of Celsus to which I refer,—namely,“ Venis enim maxime credimus, fallacissimæ rei,”*-doubtless had special reference to feverish conditions, and was meant to enforce the importance of attending to certain qualifying circumstances, but not to deter from the attempt to derive information from the pulse; otherwise he would not have added, in the same paragraph, that we know “eum non febricitare cujus venæ naturaliter ordinatæ sunt.”

The pulse or diastole of an artery is obviously produced by the contraction of the heart; and the quickness, strength, and regularity of the pulse depend on the manner in which the heart fulfils its office. It is chiefly the elasticity of the arteries which prevents a succession of jerks, and renders the flow of the blood uniform, just as the elasticity of the condensed air in the fire-engine causes a continued stream, on the principle that any intermitting motion can be converted into a continued one, by making the original force compress a reservoir or spring which keeps up a constant reaction.

Elasticity, as shown by John Hunter, is most remarkable in the large arteries, while the muscular coat is probably most developed in those of smaller calibre;- an arrangement rendered necessary by the fact, that the conjoined diameter of the small arteries is much greater than that of the large.

It will follow from these observations, that the structure, sympathies, and innervation of the heart and arteries, as well as the modifications of the circulating fluid, are all concerned in giving its character to the

* A. Corn. Celsi Medicinæ, Melligen's Edition, Edinb. 1824, p. 104.

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