Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 1.djvu/29

Rh the prophylaxis of one of the most serious diseases occurring in the Tropics.

When he wrote the chapter on Malta Fever, Bruce had already discovered the Micrococcus melitensis; but, just as was the case with Laveran's discovery, we had to wait a long time before the discovery bore practical fruit. Now, however, we know that the micrococcus is acquired in what, when Davidson's book was written, was an entirely unsuspected medium and manner. Both from a scientific and practical standpoint, Zammit's discovery that the germ of Malta fever is eliminated in the milk of apparently healthy goats is a discovery of a little more than a year's standing. It carries with it important practical results, as has already been proved.

Yet more important are the recent discoveries in regard to the still undiscerned germ of yellow fever, especially its dependence for propagation on the offices of the stegomyia mosquito and the efficiency of the prophylactic measures founded on that circumstance.

We cannot claim any definite or important advance in our knowledge of dengue; but in plague, the subject of the next chapter in Davidson's book, the role of the rat in its diffusion—so familiar to the ancients—has once more been rediscovered and more soundly established than ever, this time not by observation only but also by experiment. This is a discovery that promises to be of great practical value in the struggle against a terrible disease; its establishment on carefully observed facts is quite a recent occurrence.

We cannot claim that there has been much material advance in any of the subjects treated of in the next three chapters of Davidson's work, namely, those on Cholera, Leprosy, and Beri-beri; but, as regards the subject of the succeeding chapter, Negro Lethargy, or the Sleeping Sickness, it may be claimed truly that the whole subject, both