816 



SCIENCE. 



LN. S. Vol. V. No. 126. 



exact knowledge concerning the subjects 

 here under consideration. I cannot re- 

 frain, however, from merely referring to 

 the important role which the conception of 

 disease as in some way conservative or 

 combative in the presence of harmful in- 

 fluences has played from ancient times to 

 the present in the history of medical doc- 

 trines. "Whole systems of medicine have 

 been founded upon this conception, clothed 

 in varying garb. There is nothing new 

 even in the image, so popular nowadays, 

 representing certain morbid processes as a 

 struggle on the part of forces within the 

 body against the attacks of harmful agents 

 from the outer world. Indeed, Stahl's 

 whole conception of disease was that it 

 represented such a struggle between the 

 anima and noxious agents. What lends 

 especial interest to these theories is that 

 then, as now, they profoundly influenced 

 medical practice and were the origin of 

 such well-known expressions as vis medica- 

 trix naturw and medieus est minister naturce. 



It is needless to say that there could be 

 no exact knowledge of the extent of opera- 

 tion or of the nature of processes which re- 

 store or compensate damaged structures 

 and functions of the body or combat in- 

 jurious agents, before accurate information 

 was gained of the organization and work- 

 ings of the body in health and in disease. 

 Although the way was opened by Harvey's 

 discovery of the circulation of the blood, 

 most of our precise knowledge of these sub- 

 jects has been obtained during the present 

 century, through clinical observations and 

 pathological and biological studies. In the 

 domain of infectious diseases wonderful and 

 hitherto undreamed-of protective agencies 

 have been revealed by modern bacteriolog- 

 ical discoveries. Here, as elsewhere in 

 medicine, the experimental method has 

 been an indispensable instrument for dis- 

 coveries of the highest importance and for 

 the comprehension of otherwise inexplicable 



facts. Very interesting and suggestive re- 

 sults, shedding light upon many of the 

 deeper problems concerning the nature and 

 power of response of living organisms to 

 changed conditions, have been obtained in 

 those new flelds of experimental research 

 called by Eoux the mechanics of development 

 of organisms and also in part designated 

 physiological or experimental morphology. 

 Although we seem to be as far removed as 

 ever from the solution of the most funda- 

 mental problem in biology, the origin of 

 the power of living beings to adjust them- 

 selves actively to internal and external re- 

 lations, we have learned something from 

 these investigations as to the parts played 

 respectively by the inherited organization 

 of cells and by changes of internal and ex- 

 ternal environment in the processes of de- 

 velopment, growth and regeneration. 



In physiological adaptations, such as 

 those which have been mentioned, the cells 

 respond to changed conditions to meet 

 which they are especially fitted by innate 

 properties, determined, we must believe, in 

 large part by evolutionary factors. In con- 

 sidering pathological adaptations the ques- 

 tion at once suggests itself whether the cells 

 possess any similar peculiar fitness to meet 

 the morbid changes concerned ; whether, in 

 other words, we may suppose that evolu- 

 tionary factors have operated in any direct 

 way to secure for the cells of the body 

 properties especially suited to meet patho- 

 logical emergencies. Can we recognize in 

 adaptive pathological processes any mani- 

 festations of cellular properties which we 

 may not suppose the cells to possess for 

 physiological uses ? This question appears 

 to me to be of considerable interest. I be- 

 lieve that it can be shown that most patho- 

 logical adaptations have their foundation 

 in physiological processes or mechanisms. 

 In the case of some of these adaptations, 

 however, we have not sufficiently clear in- 

 sight into the real nature of the pathological 



