472 Second European Journey 



Johns Hopkins Hospital, lias reported a malignant growth of the 

 testicle which he traced out of the scrotum and through the vena 

 cava, in a continuous chain of tumour cells, as far as the dia- 

 phragm. The animal pathologists have drawn, I believe," he 

 suggested, 



too sharp a line of demarcation between malignant tumours on the one 

 hand, where the cells of the host-animal, acting under some unknown 

 stimulus are responsible for the tumorous growth, and granulomata- on 

 the other hand, such as tuberculosis or actinomycosis, where a visible para- 

 site is responsible for the presence of the primary tumour, and the direct 

 migrations of this parasite for any secondary tumours that may appear. 

 At bottom, I think the distinction between such a disease, for example, as 

 tuberculosis or leprosy and the malignant animal tumours is not as sharp 

 as some of the histolo<rists have been inclined to believe, but this is aside 

 from the question at issue, and only a note by the way. The host-reaction 

 is prominent in both. 



In this, Smith came close to venturing a purely medical opinion 

 but he remained a pathologist in the study of plants, interested 

 in galls and overgrowths of plants, a subject, he believed, " well 

 worthy the profound attention of animal pathologists, because 

 plants, after all, are not fundamentally different from animals, 

 and the study of their tumours may well prove just what is neces- 

 sary to throw light on the aetiology of cancers in man and the 

 lower animals." To this end, he discussed various kinds of bac- 

 terial plant diseases and infection, galls and overgrowths due to 

 insects, fungi, and other causes; and among the fungous galls 

 considered was " the cause of the West Indian fungous knot of 

 citrous fruits, recently worked out in [his} laboratory." After he 

 had returned to America, Dr. Peyton Rous, exchanging reprints, 

 wrote: " I see by the medical journals that your work has made 

 a deep impression on European observers and wish that I might 

 have been in London last summer to hear your paper." 



Paris and Vienna were Smith's two principal destinations for 

 scientific research. At Paris he visited the Pasteur Institute and 

 became acquainted with Dr. A. Besredka and Elie Metchnikoff, 

 the latter the celebrated discoverer of phagocytosis and vice- 

 director of the Institute. Besredka, himself an immunologist 

 and pathologist of illustrious calibre, was to become one of Smith's 

 closest friends and admirers among his foreign correspondents. 

 The great Dr. Pierre Paul Emile Roux, director of the Institute, 



