100 APPENDIX F 



(2). — Experiments on artificially infecting Birds with Thichostrokgylus 



After the completion of the experiments in grit starvation, attention 

 was turned to the possibility of infecting birds artificially with 

 infection Trichostrongyliis lyergracilis, the active agent in " Grouse Disease," 

 Strongyie and to the discovery of the method by which this infection is 

 effected in nature. It was obvious that no wild Grouse escaped 

 ^reatoe^^ infection, and already at Beauly Dr A. E. Shipley had, by 

 of heather. gQ^king some heather in water and centrifuging the residue, thrown 

 light upon the method of infection. 



This experiment was therefore carried out on a considerable scale, and even- 

 tually the process of infection became clear. In the chapter written by Dr 

 Leiper, the details of the early life history of the larval IVichostrongylus which 

 plays so important a part in the Grouse infection, will be found fully described. 



Having begun the investigation by centrifuging the washings of some 

 heather which had been used for packing a brace of birds in a game box, 

 and having discovered living microscopic larval nematodes in it, which appeared 

 to be true larvae of TricJiostrongylus, it was decided to make a further and 

 more systematic examination of heather from all parts of the country. 



Samples were obtained and examined from a great variety of Grouse 



moors at various heights and in different counties, and it at first appeared 



as though it would be impossible to obtain a sample of heather 



Analysis of . . . '■ 



heather which did uot Carry upon it the larvae of these threadworms, and 



samples. 



therefore the possibility of infection, disease, and death. 



Larval nematodes, many of them closely resembling the larval Tricho- 

 strongyliis in appearance, were to be found in every handful of heather picked 

 between Land's End and the Shetlands. 



That Grouse were unknown in the area from which the heather often 

 came, as, for example, from Dorsetshire, appeared at first sight to make no 

 difference whatever to the wealth of young nematodes, but gradually it was 

 realised that the great majority of the larval worms were entirely unconnected 

 with disease, and were really free living and not parasitic nematodes. 



Birds were then chosen out at Frimley for experimental feeding 



Experi- , ./ i & 



mental with food and water contaminated by the centrifuged residues of 

 the washings of heather from several selected moors. 



