Conclusions have likewise been erroneously drawn from the fact of a limb, dying when the supply of blood is cut off from it, but which circumstance serves to prove that blood is the most natural stimulus, and is essential to the perfect organization of the part; but the blood is nothing without its oxygen. Abstract heat, which is an exciting agent next in power, and you produce a like effect; mortification and death, will ensue; yet no one will pretend to say that the principle of caloric which pervades all matter is life. But let it not be supposed while I thus object to the reputed vitality of the blood, I wish either directly or indirectly to detract from the importance of its use in the animal system. Conveying the principles, which acted on by living organs form the various parts, and presuming it the most general and applicable stimulus of the body, I can still conceive its importance, and appreciate its value though itself be dependent on external agents for its essential qualities. Thus has the vital influence, passing for ages through all manner of speculations, and tortured in all the variety of fanciful inventions, been secured for a while in a doubtful repository by the ingenuity of its advocates, or the authority of names, but it now comes to be ousted from its local habitations, a dependent wanderer throughout the body, for after all its changes we find it of later days expressed in the excitability of Dr. Brown, acted on by external stimuli. “I say the excitability of Dr. Brown,” though it is asserted that many before him advanced the opinion of the dependent state of life on external substances; because I am willing to allow him the credit, at least, of being the first promulgator, and most zealous supporter of this simple hypothesis. Dr. Rush tells us in his publication on “animal life” that Dr. Cullen advanced the opinion in 1766, that the Edinburgh professor afterwards deserted it; and that _he_ (Rush) never did, but made it the foundation for many of his rules of practice, and actually advocated the doctrine in his course of lectures in 1771. And thus, we are given to understand, slept unheeded and unapplied, in the manuscript sheets of that professor, this important germ of a grand system, calculated by its simplicity to revolutionize all former theories of medicine, until by the arduous exertions of Dr. Brown an imperfect fabric was reared, serving at least to point to the right path, after enquirers. This digression will be excusable, in an attempt to fix, while adverting to the origin of, the opinion, and however the question of priority may be decided in the minds of gentlemen, whether they give credit to Dr. Cullen for the first suggestion, or to the discriminating mind of Dr. Rush as the strenuous supporter, they will not deny to Dr. Brown the merit of first publishing――of overcoming the prejudices against, and at length drawing the attention of the medical world to this novel doctrine.