128 



SCIENCE 



N. S. Vol,. XXVII. No. 682 



isms. In so doing, man, the conscious 

 organism, would assume a dominating role 

 in the world of organisms and create rela- 

 tions among living things not now existent. 

 D. T. MacDougal 



TENDESfCIES IN PATHOLOGY '■ 

 During the first half of the nineteenth 

 century the science of pathological anatomy 

 was created. Its rise was part of the de- 

 velopment in the natural sciences which 

 marked the beginnings of the intellectual 

 expansion of the century, and its growth 

 has continued unbroken up to the present 

 day. Out of the science of anatomical 

 pathology, which stands as the foundation 

 subject of those disturbances in structure 

 and function that constitute disease, there 

 arose other sciences the pursuit of which 

 has served to increase our understanding 

 of the nature of disease. Chief among 

 these are the sciences of general pathology, 

 erected on the foundation laid by the dis- 

 coveries in physiology, of pathological 

 chemistry, which has grown out of the 

 study by physiologists of the chemical 

 changes connected with the different or- 

 ganic functions, and of the discovery by 

 organic chemists of the nature and consti- 

 tution of the compounds composing the 

 organic skeleton and produced in the course 

 of organic metabolism, and of bacteriology, 

 that quickening subject, emerging Minerva- 

 like out of the epochal investigations of 

 spontaneous generation and the biology of 

 microscopic plants and animals, which gave 

 to medicine in a few pregnant years an era 

 of discovery in the domain of the causation 

 and the specific treatment of disease un- 

 paralleled in all medical history. The 

 resultant of the discoveries in the newer 

 fields of pathological knowledge constitutes 

 the period of etiological pathology which, 

 ' Address of the vice-president and chairman of 

 Section K, Physiology and Experimental Medi- 

 cine, American Association for the Advancement. 

 of Science, Chicago meeting, 1907. 



dating its beginnings from the middle of 

 the last century, is to-day the dominant in- 

 fluence affecting medical thought. It is my 

 wish to present to you briefly, as can only 

 be done in the limits of a short address, 

 certain of the tendencies in the study of 

 pathology to be discovered at the present 

 time. 



To compass this broad field superficially 

 even would demand more of your time than 

 would be permissible on this occasion, so 

 great are the activities to-day with which 

 the subjects of general pathology, biological 

 chemistry and bacteriology are being pur- 

 sued. I have, therefore, adopted a very 

 arbitrary course in the choice of subject- 

 matter to bring before your attention and 

 I have chosen to allude briefly to certain 

 fields of inquiry in general pathology and 

 to deal somewhat more fully with certain 

 newer problems in bacteriology which are 

 commanding at the moment the attention 

 of the best laboratories, and I have left the 

 fascinating field of biological chemistry to 

 be dealt with by a far abler hand than 

 mine. 



The causation of disease is manifold, the 

 reaction to abnormal influences is varied. 

 The forces which divert the normal func- 

 tions and bring disease into being are only 

 in part external, at the time of their opera- 

 tion, to the body. All parasitic plants and 

 animals, which disturb function or alter 

 structure and produce disease, are essen- 

 tially extrinsic agents of injury and have 

 been introduced from without either during 

 intrauterine life, of which there now exists 

 objective proofs, or later iti the period of 

 post-fetal existence. The many causes of 

 occupation diseases, so-called, in which we 

 recognize the introduction into the body 

 chiefly with the inspired air, but also by 

 way of the digestive tract and possibly by 

 way of other mucous surfaces and the skin, 

 of injurious foreign particles, are at present 

 only slightly understood and act not wholly, 



