84 



amongst the t3^pical " cage birds" that out of about 

 600 of these which I have examined I have found it 

 on only four or five occasions — this Parrot, a Magpie, 

 and a Toucan being the specimens in my memory at 

 the moment. Yet such is the effect of enormous 

 numbers of birds living in turn, generation after 

 generation, in the same enclosures, the same houses, 

 and the same cages, exposed one after another to 

 infection with micro-organisms originally left by an 

 inmate of long ago and since multiplied to an indefinite 

 extent, that " Dr. Seligmann has discovered that the 

 cause of " death of a number of birds is mycosis." 



This experience of Dr. Seligmann's is highly 

 important, and shows how powerful a factor is 

 environment. On the one hand more or less old 

 structures reeking with lowly organisms generated 

 under conditions the most favourable to their vigour ; 

 on the other hand birds, becoming day by day less and 

 less resistant to the attacks of these organisms by 

 reason of their environment being totally dififerent to 

 that which obtained during the evolution of their 

 respective species. 



And as with mycosis so we might expect to find 

 with avian tuberculosis, the same environmental 

 influences being of course at work in the case of the 

 latter disease as in the former one. Although in con- 

 siderably over a thousand cage and aviary birds 

 obtained from small communities, and examined bac- 

 teriologically by either Dr. Clarke or myself, not one 

 single case of avian tuberculosis has been observed, 

 yet according to a statement made to me about a year 

 ago by Dr. Hopkinson, derived from what Dr. 

 Seligmann had told him, tuberculosis had been 



