Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 1.djvu/31

Rh regarded as thoroughly established. This at least is a gain. Its complete recognition is of recent years.

There are still spurs to be won in this field of the tropical fluxes.

Almost equally important in their own line are the numerous additions to tropical helminth ology. They are far too numerous to mention on the present occasion. I might allude to one or two of them, as they are of special interest. Chief among these is Looss's discovery that the larval ankylostome obtains access to the intestinal canal by penetrating the skin on the surface of the body—a discovery suggesting possibilities which have to be reckoned with in regard to other nematodes, or even parasites in general, when we study the route by which they obtain access to the human host. The intact epidermis can no longer be regarded as the impenetrable coat of mail it was supposed to be. Leiper's experimental demonstration that the guinea-worm may be acquired through swallowing its cyclops intermediary, and also the discovery of two new and probably important parasites, Schistosomum japonicum and Amphistomum watsoni, are important additions to this department of tropical medicine. The linking up of the larval Filaria diurna with its parental form F. loa, as well as the recognition of this parasite as the cause of Calabar swellings, is a modern event.

As regards the chapter on Skin Diseases, similar advances could be credited to recent years.

The text-book of to-day has therefore to be in many respects a very different work from that of Davidson's. Besides amplification and alteration there have to be many absolutely new additions. Kala-azar, for instance, is an entirely new chapter, dealing with a subject absolutely unknown when Davidson wrote, and it is one which will soon be found to be of far-reaching importance, both practically and theoretically. The modern text-book