In Dr. Macmichael's pamphlet, consisting of thirty-two pages, and professing to be a consideration of the question, "Is cholera contagious?" we scarcely find the disease mentioned till we come to page 25; the pages up to this being occupied chiefly by a recapitulation of opinions formerly given "on the progress of opinion upon the subject of contagion;"--on the opinions of old writers as to the contagion of plague, small-pox, measles, &c.:--he would infer that whereas small-pox and certain other diseases have, by more accurate observations made in comparatively modern times, been taken from the place they once held, and ranged among diseases decidedly contagious, so ought cholera also to be now pronounced contagious! As an inducement to us to adopt this as good logic, he assures us that the list of diseases deemed contagious by wise men is on the increase--that non-contagionists are _perverse_ people, _blunderers_, and so forth! As to his epithets, it shall only be said that among the disbelievers of contagion in cholera, and certain other diseases probably reputed contagious by Dr. Macmichael, are to be found hundreds possessing as much candour, as cultivated minds, and as much practical knowledge of their profession, as any contagionists, whether they be Fellows of a College or not; but as to the statement of Dr. Macmichael, is it true that we have been adding to the list of contagious diseases? Not within the last fifty years certainly. Even the influenza of 1803 was, if I mistake not greatly, termed, very generally, "infectious catarrh," but what professional man would term the influenza of 1831 so? Are there not yet remaining traces of the generally exploded doctrine of even contagion in ague, at one time attempted to be maintained? M. Adouard, of Paris, still indeed holds out. Do we not know that Portal, at one period of his life at least, would not, for fear of "infection," open the body of a person who had died of phthisis? Where is the medical man now to be found who would set up such a plea? or where, except in countries doomed to eternal barbarism, are patients labouring under consumption avoided now, as they were in several parts of the world at one time, just as if they laboured under plague, and all for the simpleton's reason that the disease _often runs through families_? What disinterested man will, on due examination of all that has been written on yellow fever, stand up now in support of its being a contagious disease, of which some thirty or forty years ago there was so general a belief? On croup, and a few more diseases, many still think it _wise to doubt_. Is dysentery, known to make such ravages sometimes, especially in armies, considered now, as at one time, to be contagious? If Dr. Macmichael's pamphlet was intended altogether for readers not of the profession, _which seems very probable_, his purposes will perhaps be answered, at least for a time, but I do not see how it can make an impression on medical men.