235 



Descending from the general to tlie particular, let 

 me here give an instance of this comparative imnumity. 

 In the summer of 1901 I bought a ver}' fine example 

 of the Plumbeous Finch {Sperjiiophila plwnbca). He 

 was evidently of a good type of "disease resister," for 

 he had been on our side of the water for onl}^ a month 

 or six weeks and was in full song within half-an-hour 

 of his delivery to me by the railway people. One of 

 my outside aviaries, where of course he got no ^%% 

 food, was then his home till the Jiuie of 1902, when 

 an idea struck me that as he was so strong and lusty 

 here was a good opportunity for me to try a new 

 departure in the way of hybrid breeding. So a small 

 hen Canary was picked out from among my lot, and 

 together with the Finch transferred to a breeding cage 

 indoors. At that time I myself was not altogether 

 emancipated from the thraldom of tradition and 

 superstitious beliefs, and therefore with the usual 

 pretty idea of "building up" my prospective breeders 

 — (this always looks so alluring on paper) — I gave them 

 the regulation ^%% food in the regulation quantities. 

 The non-immunized wild bird from being active, 

 salacious, and full of song, almost immediatel}^ became 

 mopey, thickened, and dull, and was dead in a fort- 

 night from acute enteritis accompanied with diarrhoea 

 and fits. The Canary, belonging to a partially immu- 

 nized race, survived and, I believe, is still alive as I 

 write these lines. She, it will be seen, was a counter- 

 part of the Englishman belonging to a race partl}^ 

 immunized against tuberculosis. 



The explanation of this comparative immunity of 

 the Canar}^ is also to be found in the natural law 

 already alluded to, viz. that it is conferred by long 

 contact with the disease on the part of the race, 

 combined as a consequence with ruthless and 

 persistent elimination thereby of the most unfit 

 individuals of that race. Exactly how long the Canary 



