Last, but most important of all, a thorough search must be instituted for _tophi_, not only in the ears, but elsewhere. If anything could emphasise the indispensable _rôle_ played by _tophi_ in the diagnosis of gout, it would be our utter inability to effect in their absence a diagnosis of these _acute_ types of _gouty polyarthritis_. The establishment of the existence _in situ_ of such _articular uratic deposits_ disposes forthwith of all possible doubts as to the true nature of the case; but if, as so frequently happens, the tophi when present are of _ab-articular_ site, then we must withhold our decision pending the exclusion of certain other joint disorders, to the differentiation of which we now proceed. DIFFERENTIAL DIAGNOSIS The class of disorders that call for discrimination are those of infective origin. In the first place, _acute articular rheumatism_ must be excluded; nor is it less necessary that we should eliminate _gonorrhœal_ and _syphilitic_ types; while, last, but not least, that vast group, the _undifferentiated infective arthritides_, is but too often a source of confusion. ACUTE ARTICULAR RHEUMATISM Unquestionably many cases of _acute gouty polyarthritis_ have been confounded with _acute articular rheumatism_, and _vice versâ_. Garrod on this point remarks: “That many cases of acute gout have been mistaken for acute rheumatism I do not doubt, and, on the other hand, that some few cases of acute rheumatism have been regarded as of a gouty nature I am no less certain. I may refer to the oft-quoted case related by Dr. Haygarth in which gout was supposed to have been transferred from the extremities to the heart as an example of the latter error.” It is only, of course, with that type of acute gouty polyarthritis accompanied by _pyrexia_, and not the _afebrile_ variety, that confusion with acute articular rheumatism is possible. What then are the points of discrimination? ACUTE ARTICULAR RHEUMATISM. ACUTE GOUTY POLYARTHRITIS. Age and sex Most common between ages Maturity and old of fourteen and thirty. age. Males. Predominance of males Females markedly after twenty. exempt. Heredity Very disputable. Very pronounced. Onset Usually abrupt and often Insidious, with with tonsillitis. premonitory gastro-intestinal symptoms. General symptoms High fever, sometimes Moderate pyrexia. hyperpyrexia. Profuse Marked daily acid sweats. remissions.