36 Transactions. — Miscellaneous. 



again like indianibber softened by heat. The full significance 

 of .this discovery could not be perceived at the time. The fields 

 of physiology and pathology were still practically unexplored, 

 and the migration or diapedesis of the blood-corpuscles could 

 only be registered as a fact to be made use of on some future 

 occasion. It was one of those discoveries which prove the value 

 of the pursuit of knowledge for its own sake, the scientific 

 worker, with far-seeing vision, looking forward to the time 

 when facts apparently isolated, and to the untrained mind of 

 little value, will find their connection with other facts and 

 form a continuous chain of knowledge. 



Dr. Addison's discovery was lost sight of for nearly a quarter 

 of a century, when the migration of the white corpuscles was 

 rediscovered by Cohnheim (1867), who studied the process of 

 inflammation in the mesentery of a frog, and added valuable 

 newly-observed facts to the pathology of inflammation. Now, 

 what could impel these white corpuscles to wander out from 

 their natural element ? Were they driven by the vis a tergo 

 with the blood-stream? What are these white cells'? Here, 

 however, we must leave them for a time, as a novelist some- 

 times leaves important characters introduced in his earlier 

 chapters, while others occupy the scene, to bring them all 

 together for the denouement at the end. 



A few words more concerning theories of disease, and I 

 shall be able to enter on the more immediate subject of this 

 address. The origin of fevers has at all times exercised the 

 minds of physicians. Even up to quite a recent period, twenty 

 years ago, there were some who maintained, and there may be 

 still, for aught I know, some who believe, that certain fevers — 

 typhus and typhoid, for instance — could be generated de novo, 

 and without infection, direct or indirect, from an individual 

 sufi^ering from fever, by privation, fatigue, dirt, and overcrowd- 

 ing. This is the doctrine of heterogenesis from the clinical 

 side. On the other hand, there were some, even as long as 

 fifty years ago, who believed that a specific poison was handed 

 down by descent from a similar poison, and was received into 

 the system, where it multiplied and "fermented," and was 

 finally cast out by a crisis. It was the old doctrine of crudity, 

 coction, crisis, and despumation a little farther advanced. 

 The theory of an impure state of the blood gave place to one 

 more definite — namely, that of a specific organic body as the 

 poisoning agent — but it was understood that this poison 

 was spread, and infected human beings, by means of the 

 atmosphere. I am indebted to Dr. Aitken's work on medicine 

 for the fact that in 1838 Boelim attributed cholera to the 

 presence of a fungus affecting the intestinal epithelium, and 

 he gave drawings of microfungi which he found. These 



