Decembeb 26, 1902.] 



SCIENCE. 



1011 



laboratories, and both the nature of im- 

 munity and the best method of accomplish- 

 ing it, which have puzzled medicine so 

 long, bid fair to become known in the near 

 future. With this achieved, preventive 

 medicine will have gained one of its great- 

 est triumphs. 



A word should here be said regarding 

 two of the infectious diseases whose pecul- 

 iar method of transmission, long a mys- 

 tery, has now become known. I refer to 

 malaria and yellow fever. The able work 

 of Laveran, Manson, Ross, Grassi, Koch 

 and others on the former, and that of Reed 

 and other courageous Americans on the 

 latter, have demonstrated conclusively 

 that these diseases are transmitted from 

 man to . man through the aid of the 

 mosquito, which, receiving the germ from 

 an infected individual, cultivates it within 

 its own body and later delivers it in a 

 properly prepared form to another unfor- 

 tunate human being. Moreover, it is en- 

 tirely probable that this is the sole method 

 of the transmission of these diseases. The 

 ounce of prevention here consists in : first, 

 eliminating, from the community, so far 

 as possible, the breeding places of the 

 mosquito; secondly, totally preventing, by 

 simple screens, the access of the insect to 

 each case of the disease. By the employ- 

 ment of these simple methods in Havana, 

 during the year ending with the end of 

 last September, not a single case of yellow 

 fever originated within the city, an event 

 unparalleled in recent times. The active 

 work now being carried on by the Liver- 

 pool School of Tropical Medicine on the 

 west coast of Africa bids fair to -reduce 

 materially the extent of malarial fever, so 

 long the scourge of that region. 



It is impossible to predict the full out- 

 come, in the future, of the diligent research 

 of the past few decades in the field of the 

 infectious diseases. Certain it is, that in 



civilized countries there appear no more 

 the terrible epidemics of the past, such as 

 the Black Death, which, in the fourteenth 

 century, ravaged much of the continent of 

 ^Europe, and in England swept away more 

 than half a population of three or four 

 millions. The struggle of the deadly 

 germs for existence is becoming daily a 

 more desperate one. Just as paleontology 

 has revealed numerous instances of the an- 

 nihilation of once flourishing species of 

 organisms high in the scale of life, it is 

 perhaps not visionary to look forward to 

 the ultimate extinction of these more lowly 

 forms, and, with them, to the abolishment 

 forever from the face of the earth of the 

 diseases which they cause. 



The study of the microorganisms in the 

 past and present bears upon a much wider 

 range of subjects than the immediately 

 practical one of the prevention and cure 

 of individual diseases, however important 

 that may be. It is constantly aiding, in 

 ways surprising and unforeseen, in the so- 

 lution of even long-standing and remote 

 problems. I need only mention here that 

 of the recognition of human blood as dis- 

 tinguished from that of lower animals. 

 Moreover, this study has helped in the 

 elucidation of many of the fundamental 

 problems of protoplasmic activity, and has 

 given men of medicine a broader ciilture 

 and a higher outlook over the accomplish- 

 ments and possibilities of the human or- 

 ganism. This cannot fail to react upon 

 other fields than that of the infectious dis- 

 eases, to malce treatment in general a more 

 rational matter than it has ever been, and 

 to uplift the whole science of medicine. 



Before finally leaving this subject, I 

 would speak of the many instances of per- 

 sonal heroism exhibited by the men who 

 have labored in this field. The records 

 teem with stories of those who, recognizing 

 more fully and intelligently than others 



