At the very commencement, he hits on a great cause of evil, and boldly assails one of the most mischievous of all conventionalisms. "The division of medicine and surgery," he observes, "is mischievous, as directing the attention of the two orders of practitioners too exclusively to the diseases usually allotted to them." There is indeed no exaggerating the evils of that partial mode of investigation to which such a custom almost necessarily leads. We fall into error, not because of the difficulty of the subject, but because we never can, by looking _at one set of diseased processes only_, learn the whole of the facts belonging to the subject. It was just this that prevented Fordyce from arriving at correct views of fever. Nothing could be more excellent than the way he _began_ to consider it; but he hardly begins, before he tells us that he intends to exclude those febrile affections which fall under the care of surgeons. In doing this, he at once abandoned a series of facts which are absolutely essential to the investigation. It must be obvious, on a moment's reflection, that, if a particular condition of a part have a relation to the whole body, the study of one without the other, or even if both be taken up by different persons, nothing but the most imperfect views can result. A jury, still more a judge, might in some cases guess from partial evidence the issue of a legal investigation; but who ever heard of either determining beforehand to examine a portion only of that evidence? Yet it is not too much to say, that hardly any legal question can be so recondite as many inquiries in physiology. The nature of the case is always more or less obscured by a number and variety of interfering circumstances. Diseases may be regarded, in fact, as nothing more than natural laws, developed under _more or less complicated circumstances of interference_. Lord Bacon had warned all investigators of Nature of the danger of attending only to a portion of the facts; it had been one of the great bars to progress of knowledge in general. I regret to say that it still continues the bane of _almost all medical inquiries_. Abernethy's inference in relation to this mutilated sort of investigation is too true, when he observes that "the connection of all local diseases with the state of the constitution has obtained little notice;" whereas the truth is, that "no part of an animal body can be considerably disordered without affecting the whole system." Now here Mr. Abernethy claims—what? Simply this: he claims for _function_—that is, _the various offices fulfilled_ by the several parts and organs of the body—that which Cuvier has so beautifully insisted on, and which our own Owen has so instructively exemplified in regard to _structure or formation_; namely, a _necessary relation_ between the whole and all its parts.