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XXXVII] Against its being of a tuberculous nature is the circumstance that it is confined to the tropics. Against its being syphilis is the practical absence of syphilis among the natives of Fiji, where this form of ulceration is particularly common. Against its being a sequel of yaws is the want of correspondence in the proportional prevalence of the two diseases; for, although ulcerative rhino-pharyngitis is common in some places in which yaws is common, it is rare in other places where yaws is common, and common in other places where yaws is rare. For these and other reasons Leys has thrown out the suggestion that destructive rhino-pharyngitis of the tropics is an independent disease produced by a special micro- organism as yet undetected, and not, as has been supposed, a sequel of yaws. On the other hand, it may be a form of buccal leishmaniasis.

Mortality.— Although in the literature of the subject reference is made to deaths from yaws, yet, judging from the statistics collected by Nicholls, the mortality must be very small indeed. In 7,157 West Indian cases, treated in various yaws hospitals, there were only 185 deaths— a mortality of 25.8 per thousand; a death-rate, as Nicholls points out, less than the average annual death-rate in one of the islands —Antigua. Doubtless, although yaws itself seldom proves directly fatal, intercurrent diseases, such as sloughing phagedæna and phagedænic ulceration, predisposed to by the skin lesions, occasionally do so.

Morbid anatomy and pathology.— No visceral changes have been found peculiar to yaws, although, of course, when yaws concurs with syphilis, gummata, etc., may be found; in this case the concurrent gummata may belong to the syphilitic and not to the yaws infection. An important point of contrast in the respective morbid anatomy of yaws and syphilis is the absence of endarteritis in the former and its frequency in the latter.

The tumours on the skin are granulomata made up of round or spindle-shaped cells, held together by a small amount of connective tissue and abundant blood-vessels. The focus of the circumscribed cell