August 18, 1905.] 



SCIENCE. 



201 



vidual. It needs no extended argument to 

 demonstrate the sociological effect of the 

 recognition and removal of this one cause . 

 of disease. Nor will any one doubt the 

 desirability, yes, the necessity, for a careful 

 investigation into the life history and ef- 

 fects of these parasites. For from the life 

 cycle is to be obtained the clue to the means 

 of attack, to the weak spot in the armor of 

 the disease on which its ultimate destruction 

 depends ; and every one recognizes as the 

 ultimate goal of medicine as a science the 

 eradication of such diseases that the phys- 

 ical man may move forward toward the 

 possibilities in perfect development with 

 which he is endowed. 



That which I have outlined has been 

 known in part for many decades, even 

 though the investigations of recent years 

 have contributed much toward a clearer 

 comprehension of the question. Among 

 the Protozoa, however, the last few years 

 and even months have brought discoveries 

 of the most startling character regarding 

 their relation to disease. It was in 1890 

 that Laveran first discovered the amoeboid 

 parasite in the red blood cells now univer- 

 sally recognized as the cause of malaria, 

 and not until 1899 was its life history 

 clearly outlined, while even yet some minor 

 details of the picture are lacking. Since 

 the opening of the new century there has 

 come the demonstration of the cause of 

 sleeping sickness, a terrible disease of trop- 

 ical Africa, in a flagellate protozoon {Tryp- 

 a7iosoma) other species of which in the 

 blood of various domestic animals have 

 been shown to give rise to widespread and 

 fatal epidemics in other countries; the 

 parasite of smallpox has been found to 

 belong to this same group and its life his- 

 tory has been determined partly at least. 

 The disease known as kala-azar, dum-dum 

 fever, or splenomegaly, a fatal malaria-like 

 malady of India and Africa, has been 



traced to another protozoon parasite ; in 

 yellow fever it seems probable that such 

 organisms are the exciting cause ; in various 

 other diseases they have been seen, even 

 though in some cases subsequent investiga- 

 tion has failed to demonstrate the parasites 

 and confirm the reports ; and finally within 

 this year accounts by well-known German 

 investigators proclaim the discovery of the 

 cause of syphilis in a hitherto undiscovered 

 protozoon of the order of flagellates. In 

 all of these maladies the bacteriologists have 

 been searching with great care for the etio- 

 logical factors, but their efforts have been 

 fruitless. It is apparent that the new field 

 will demand its own technic, and until that 

 has been developed and the proper stand- 

 ards of judgment formulated, much work 

 will necessarily go to waste and many errors 

 be committed. 



These organisms, the unicellular animals, 

 are distinctly analogous to the unicellular 

 plants, among which the bacteria stand as 

 the characteristic disease producers. In- 

 deed, the recent studies have shown that one 

 genus, Spirochcete, long known and hitherto 

 classified among the bacteria, is probably 

 not such, but rather a flagellate protozoon. 

 And possibly other genera of Protozoa are 

 also wrongfully assigned to bacteria. On 

 the other hand, zoologists have long recog- 

 nized certain forms of Protozoa as patho- 

 genic, producing disease among the various 

 other animals, and this is at least an indica- 

 tion of their filling a similar role in the 

 human body. 



In consideration of these facts it is not 

 unreasonable to believe that we stand now 

 at the opening of a new field which is to 

 make of itself in the future what bacteriol- 

 ogy has made in the last half century. 

 There is need of a Pasteur, a Koch and 

 their confreres to lay the foundations 

 strongly and to analyze with equal sharp- 

 ness the relation of these animal micro- 



