304 



SCIENCE 



[N. S. Vol. XLVII. No. 1213 



that no sj-stem of recruiting the workers 

 could keep pace with the destruction of hu- 

 man life wrought among them by these dis- 

 eases. 



One should not pass without notice a 

 group of protozoal and bacterial diseases 

 transmitted by insects, such as sleeping sick- 

 ness, bubonic plague and the various re- 

 lapsing fevers, all of which owe their spread 

 in nature exclusively to inoculation by bed- 

 bugs, ticks and biting flies. The significance 

 of scientific discoveries which have led to 

 formulation of measures for the control of 

 such diseases may be estimated in correct 

 propositions when one bears in mind that 

 at a very recent date malaria has claimed in 

 Italy alone 200,000 victims annually, sleep- 

 ing sickness 500,000 in Africa and plague in 

 India has often destroyed more than a mil- 

 lion victims in the course of six months. 

 Among those who have contributed promi- 

 nently to the study of these organisms and 

 to the solution of the problems of the dis- 

 eases they produce must be named the zool- 

 ogists Minchin and Fantham ; of the work 

 done on the insects that transmit such or- 

 ganisms appropriate mention is made by 

 another speaker in this symposium. 



Not less significant is the story of the 

 hookworm and its ravages, which have ex- 

 tended over every part of the globe in trop- 

 ical and subtropical regions and have justi- 

 fied the organization of a great philan- 

 thropic movement to combat them. The 

 first great step in advance in the handling 

 of this problem was taken when at the In- 

 ternational Zoological Congress in Berne, 

 Switzerland, the zoologist Looss demon- 

 strated before a critical and unbelieving 

 audience the intricaite story of the migra- 

 tions of this parasite and its mode of gain- 

 ing entrance to the human host. Previous 

 to that time, no effective measures for com- 

 bating the disease had been worked out, 

 save tine procedure of albandoning infected 



teiTitory which was in itself a clear con- 

 fession of inability to cope with the diffi- 

 cultj'. As a direct result of the definite 

 knowledge cofiteerning the life history of the 

 parasite and its point of aittack upon the 

 human system, a code of procedure has 

 been worked out so definitely that its intro- 

 duction is in fact resulting in the elimina- 

 tion of the disease from human considera- 

 tion. Foremost among those who have 

 aided in achieving the brilliant results of 

 the campaign against the hookworm stands 

 the name of the zoologist Stiles. 



When the city of Manila came under the 

 control of the United States of America, one 

 in four, if not one in three, of all the deaths 

 occurring in its limits were due to the attack 

 of the parasite of amebic dysentery. "While 

 it is premature to say that this problem has 

 been solved, still, studies on the structure 

 and life historj^ of this and similar forms 

 by the zoologist Schaudinn and others have 

 contributed such information concerning 

 the life history and the effects of this para- 

 site as to indicate successful lines of de- 

 fense against its attacks and to reduce 

 greatly the toll of human life it exacts. 



But these items do not indicate the ex- 

 tension of knowledge regarding such organ- 

 isms. Even among the higher parasites 

 studies of recent date have added to the list 

 of forms that menace man several intestinal 

 flukes, three blood flukes, a number of tape- 

 worms and various roundworms, and there 

 is no reason to think the list is complete. 

 Each form demands an individual study of 

 its structure, life history and habits before 

 definite measures can be formulated for 

 protection against its attacks. To recount 

 all that has been done in the many cases 

 would transcend the possible limits of this 

 paper. A very large part of the significant 

 information regarding these forms has been 

 furnished by zoologists. When, however, 

 protozoan parasites are taken into consid- 



