Page images

plative, and perhaps more credulous character, who have been disposed to believe that there were invisible causes, operating to produee the alterations which are visible, and, who from much less numerous facts have drawn the same inferences that I have done. And many of these, from Pythagoras downwards, have expressed their sentiments, though with some variety, yet pretty much to the same effect. The Greek philosophers recognized in man, the we, *x, and Neo, the body, vital principle, and mind, whilst some used words significant of intellect, to express the energizing principle in nature, without apparently having any clear ideas of intelligence.

What was called the Anima Mundi, was, however, by many considered as a distinct and active principle, and was not confounded with intelligence of any kind. I know not how I can better exhibit to my au

dience the subject I am alluding to, or better acquaint them with the general tenour and tendencies of these opinions, than by quoting that portion of these philosophical notions, which Virgil is said to have put into the mouth of Anchises,

Spiritus intus alit, totamgue infusa per artus

Mens agitat molem, & magnose corpore miscet.

And please to observe, gentlemen, it is Virgil says, it is Anchises speaks, that which I also this day have been saying;

Inde hominum pecudumque genus, vitaeque volantum
Et quae marmoreo fert monstra sub acquore pontus. -

[ocr errors]


I proceed to speak of the structure and functions of the nervous fibres. The nerves which we observe pervading the body, appear to be packets of very minute threads, seemingly distinct from each other. The nerves divide and subdivide, and in so doing a certain number of threads separate from the original packet, and appear as a distinct nerve. It is, therefore, possible to trace a minute nerve, up to its origin, from the toe or finger, by splitting it off from the various packets with which it has been conjoined. So far does anatomical fact concur with the physiological opinion,

that every nervous filament communicates distinctly with the brain or some process of that organ.

This apparent continuity is, however, lost, whenever we find those intumescences on nerves which are called ganglia, for in these there seems to be a mixture or consolidation of the nervous matter. It is also lost wherever various nerves unite together, and form; a plexus; in which case the nervous fibrils either coalesce, or become inextricably interwoven with one another. . . . . . . . . . . . . . . - .. - ‘. . . . . . . . . . ; : The nerve from which the thoracic and abdominal viscera are chiefly supplied, is beset with numerous ganglia and Plexuses; and as we cannot by our will influence the actions of those viscera, and as the iris, the motions of which are also involuntary, is supplied with nerves from a ganglion, it has been thought that ganglia, by intercepting the direct communications between the brain and the extreme branches of nerves, might render parts thus supplied less amenable to the will, and less under the influence of the general affections of the nervous system. It is also thought... that ganglia might serve the office of subsidiary brains, each , affording a separate source of nervous energy. •

On the one hand, it ought to be observed, that all the vertebral nerves, supplying parts over, which the will exerts the most perfect control, have ganglia at their commencement; and that the nerves of the leg and arm form a plexus near their origin. The actions of the cremaster muscle are involuntary; yet I believe it is supplied by the same nerves, which supply muscles that are subject to wor

« PreviousContinue »