200 THE GROUSE IN HEALTH AND IN DISEASE 



this transparent tapeworm, but as a general rule the cystic forms of 

 this genus live in some insect or myriapod (centipede), as is shown by the 

 fact that this genus of tapeworm occurs in bats, insectivores, rodents, 

 and insectivorous birds. One species, Hymenolepis nana, occurs in man, 

 most frequently in children, and is not at all uncommon in Italy. 

 Sporadic cases of another species, H. diminuta, occurring in man, are 

 also recorded. There is some evidence that the larval stage of this 

 last-named species, which is common in rodents, occurs in the flea. 



FIG. 17. Hymenolepis microps. 



The injury caused by the presence of this tapeworm is serious, and 

 when it is present in certain numbers it is associated with the occurrence 

 of bacteria in the tissues, the number of which bears some direct propor- 

 tion to the degree of infection of the tapeworms. That the latter should 

 disappear during the winter is a curious fact which requires elucidation. 



NEMATODA. Threadworms or Round Worms, 

 (i.) Fam. TRICHOSTRONGYLID^. 



XII. Trichosirongylus pergracilis (Cobb. 1 ). 

 (The Strongyle of the Grouse.) 



This is the second parasite worm discovered by Cobbold and 

 described by him in 1873. 2 It belongs to a genus peculiarly destructive 

 to birds. Some details of the harm caused by its near allies have been 

 given in the Report of the Committee. 



The strongyle lives in the opaque fluid contents of the paired cseca 

 of the Grouse. It is very thin and fine, and is difficult to see when 



1 Synonym : Strongylus pergracilis, Cobb. 



2 The "Grouse Disease," The Field Office, London, 1873. 



