218 THE GROUSE IN HEALTH AND IN DISEASE 



pheasants. It occurred in the hand-reared birds at Frimley, and Dr Cobbett and 

 Dr Graham-Smith have found twenty-three in one caecum and ten in the other in 

 a Grouse from Abbeystead which was free from T. pergracilis, and one in each 

 ceecum of a Grouse from Longtown, Cumberland, which had one hundred and 

 eight T. pergracilis in one caecum and one hundred and twenty-seven in the 

 other, and the same number similarly distributed in a bird from Bolton Abbey, 

 which had three thousand one hundred and eighteen T. pergracilis in one csecum 

 and two thousand eight hundred and seventy-seven in the other. 



(IV.) Family Filariidae. 

 (v.) FILARIA SMITH; (Sambou.) 



Dr Sambon * has described a microfilaria or larval form of some species of 

 Filaria in the blood of Grouse. The adult forms of such larvae usually live in 

 the lymphatics and subcutaneous tissues ; their larvae pass into the blood, and 

 are conveyed to new hosts by some blood-sucking insects. 



PART II. ON THE DEVELOPMENT AND BIONOMICS OF TRICHOSTRONGYLUS 



PERGRACILIS 



By Dr Robert T. Leiper 



In view of conclusive evidence accumulated by the Inquiry regarding 

 the constant presence of a small threadworm Trichostrongylus pergracilis in 

 the caeca of nearly all sick adult Grouse, it became a matter of importance to 

 study in some detail the life-history of this parasite with a view to determining 

 the manner in which it is reproduced and disseminated, the mode of infection of 

 healthy birds and, if possible, to obtain experimentally the symptoms of " Grouse 

 Disease" under artificial conditions. In order also to have some reasonable 

 basis of fact upon which to establish preventive and curative measures, a 

 knowledge of the conditions favourable to and inimical to the growth of the 

 parasite at its various stages of development became necessary. The present 

 section deals with the results of an inquiry into these problems. 



The parasites are exceedingly fine hair-like worms of about one-third of an 

 inch in length, and of a pale pink colour, but of such transparency as to be almost 



1 See "Journal Tropical Medicine and Hygiene," x, p. 304, 1907. Filaria smithi cannot, however, stand 

 as the name is preoccupied by Cobbold's species, Filaria smithii, from the elephant. Transactions of the 

 Linnixan Society of London, 2nd. 



