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diseases, the knowledge of the life-history of the pathogenic micro- 

 organisms, the discovery of the portals through which they gain 

 entrance to the animal economy, and the conditions under which 

 infection occurs, have brought to us material powers to prevent 

 and protect. The first great result of this new knowledge was the 

 development of antiseptic surgery and all that it represents. But 

 apart from this we have but to remember what has been gained 

 by a scientifically evolved prophylaxis against tuberculosis and 

 typhoid fever to reflect upon how far cholera and plague have 

 lost their terrors to contemplate the brilliant results of the dis- 

 covery by Ross and the Italian school of the life-history of the 

 malarial parasites as manifested in the anti-malarial campaigns 

 carried on in various regions by Koch, and in Italy by the Society 

 for the Study of Malaria, a noble institution, of which our Latin 

 brothers may well be proud, and lastly to look upon the bene- 

 ficent and far-reaching influence of the recent work of Reed and 

 Lazear and Carroll and Agramonte with regard to yellow fever, 

 to realize what bacteriological and parasitological studies are doing 

 for preventive medicine. 



But beyond this external prophylaxis, the studies of the pro- 

 blems of immunity, beginning with Pasteur's inoculations against 

 anthrax in 1881, have given us, so to speak, an internal prophy- 

 laxis, a functional prophylaxis, if one will, in the possibility of 

 producing a greater or less degree of individual immunity, such, for 

 instance, as is now possible in diphtheria, cholera, plague, typhoid 

 fever, and dysentery. 



The enforcement of scientifically planned and accurately de- 

 duced prophylactic measures has become to-day one of the main 

 duties of the practitioner of medicine. It is as much the task of 

 the physician nowadays to guard over the disposal of the sputa 

 of his tuberculous patient, of the excreta of the sufferer from ty- 

 phoid fever, or cholera, or dysentery, as it is to attend to the im- 

 mediate wants of the invalid. How rapidly has the exact replaced 

 the conjectural in this branch of medicine! 



But while diagnosis and prophylaxis were being removed from 

 the domain of conjecture to the field of exact observation, and 

 reason, and research, while the possibilities of surgery were rapidly 

 widening through the discovery of anesthesia and the introduc- 

 tion of antiseptic methods, medical treatment, until the last two 

 decades, still remained largely empirical. The development of 

 exact clinical methods of observation and the statistical tabula- 

 tion of experience for which we are especially indebted to Laennec 

 and Louis, and their followers, gradually brought about, to be 

 sure, many advances, while a large number of useful therapeutic 

 agents introduced by the newly developed science of pharmaco- 



