470 DR. p. CHALMERS MITCHELL ON LONGEVITY AND 



improve in general vitality and in the quality of their hair, fur, 

 or feathers. Their viability is in a large measure determined by 

 their power of resistance to bacterial and probably other parasites. 

 It is impossible to ward off infection altogether, but the general 

 condition of the body and exposure to light and air are the most 

 certain preservati\es. 



It appears to be certain that although infection by a very few 

 parasites (microscopic or macroscopic), as these are living 

 creatures with the power of reproduction, is theoretically 

 enough to contaminate an animal, yet, in actual practice, a fairly 

 heavy bombardment of parasites is necessary. Confinement in 

 heated houses not only weakens the natural power of resistance, 

 but affords the greatest opportunity for heavy bombardment. 

 Exposuie to cold, light and air rapidly destroy a vast proportion 

 of the parasites or their eggs or embryoes that are not in actual 

 occupation of their host, and warmed houses afford the best 

 possible environment for them. I do not doubt, that by reducing 

 artificial heating as much as possible, and by making the shelters 

 as small and as easy to clean as possible, the damaging effect of 

 parasitic infection could be reduced enormously. 



AVES. 



PASSERES. 



TURDIDJE. ^°-.°^' 



Tiirchis, whole genus 68 



T. cdhiventris (White-bellied Thrush). 2 



T. cardis (Grey Thrush) 2 



T. falklandicus (Falkland Island 1 



Thrush). 



^T.j'Zfmj'jes (Brazilian Grey Ousel) ... 1 



T. iliacus (Redwing) 9 



T. leuconielas (Brown Thrush) 5 



T. onet'tda (Blackbird) 7 



T. migratorius (American Robin) 11 



T. musicus (Song- Thrush) 4 



T. tmistelinus (Wood-Thrush) 4 



T. 20<x:cilopterus (Grey- winged Blackbird). 1 



T. pilaris (Fieldfare) 8 



T. rufiventris (Red-bellied Thrush) ... 3 



T. torquatus (Ring-Ousel) 5 



T. tristis (Sorry Thrush) 2 



T. viscivorus (Missel Thrush) 3 



Geocichla citrina (Orange-headed Ground 2 



Thrush). 



G. wardi (Pied Ground Thrush) 1 



Monticola cyanus (Solitary Thrush) ... 7 



M. saxatilis (Rock „ )... 6 



Myiophonus horsfieldi (Horsfield's 1 

 Whistling Thrush). 



