That diseases, like their victims, alter with environment is but too clear. Who can doubt that the gout of the Regency has to-day assumed a milder clinical _facies_? Physicians of those days were haunted with the fear of confounding it with _erysipelas_ and _phlegmon_. Still, while no such fears apparently beset us to-day, it were well to walk circumspectly. Thus, recently a friend of mine came across an instance of what he deemed _acute gout_ in a _metacarpo-phalangeal_ joint. Its failure to respond to colchicum and the growing intensity and extent of the local inflammation suggested incision, when, lo, pus issued, to the subject’s comfort, but to his own chastening! There are, however, many more likely sources of fallacy, these, too, of the most diverse type, inasmuch as they differ according to the exact location in the foot of the assumed gouty process. For while the _big toe_ is the _site of predilection_ for the _initial_ manifestation, it is not always so. The _primary_ outbreak may be located in any of the smaller joints of the foot, or outside them in related structures: in the _heel_, the _sole_, or the _tendo Achillis_. These vagaries greatly enhance the difficulties of diagnosis. For the process of differentiation will vary according to the particular joint or structure involved, the predilections of certain infective processes, not to mention the marked liability of the foot to painful disturbances of static origin. DIFFERENTIAL DIAGNOSIS Inasmuch as the primary outbreak may be located in any part of the foot, we purpose, for reasons just cited, dealing _seriatim_ with gout in (1) the big toe; (2) the instep; (3) the heel; (4) the sole. GOUT IN THE BIG TOE _Infections._—There is no _â priori_ reason why any of the infections may not find a nidus in the _first metatarso-phalangeal_ joint. Thus, Garrod, as we know, held gouty subjects specially liable to _pyæmia_. In rare instances, the primary focus has been in or near the _great toe_, and has consequently been mistaken for _gout_. The rapid progress of the disease would of course soon clear up the nature of the case. But if the subject has previously suffered from gout, such a diagnostic error at first sight is quite excusable. Accordingly, as a safeguard in all doubtful cases, inquiry should be made as to the existence of _bladder_ troubles, _piles_, etc., especially _any recent operation_ in this or other regions. Again, while gout in its _articular_ form is rarely, if ever, met with in children, it must be recalled, on the authority of Sir James Goodhart, that _rheumatism_ in their instance is occasionally limited to _one_ joint. Moreover, this distinguished physician actually saw it localised in the _great toe_, “in a case in which the subsequent course of the disease showed that it was acute rheumatism.”