" GROUSE DISEASE "—STRONGYLOSIS 20^ 



that Strongylus tennis Eberth of the goose should also be reckoned as a species 

 of Trichostrongylus was made to me by Dr R. T. Leiper. 



Specimens of T. pergracilis are found in the caeca of most Grouse. They are 

 apt to cover themselves with mucus and dirt, and are consequently hard to see 

 and often overlooked. We have found them, with hardly an exception, in every 

 one of the two thousand Grouse examined.^ They are rendered opaque and 

 white, and hence much more apparent, by shaking up the contents of the csecum 

 in 75 per cent, alcohol, to which a few drops of corrosive sublimate have been 

 added. Their presence is also readily detected by compressing a drop or two of the 

 caecal contents between two microscope-slides and holding them up to the light. 

 The worms, if there be any, then appear as thin, white, transparent lines. We owe 

 this method to Dr Wilson. 



T. pergracilis is an extremely fine worm, measuring in the male on the 

 average 6 to 8 mm., and in the female 8 to 10 mm. They are very narrow and 

 hair-like, and, as a rule, whitish in colour, but sometimes have the tinge of blood 

 when seen in a very thin layer on a slide through the microscope. They are very 

 transparent, readily revealing their internal structure, and they are so soft that the 

 pressure of a cover-slip almost always ruptures them. The cuticle is very clearly 

 and definitely ringed, and the rings are so constituted that whilst the worm can 

 easily work its way forward through a tissue, it would have diflficulty in wriggling 

 backward. The rings give the edge of the body a strongly serrated appearance 

 like a saw. This is most marked a little way behind the head, and extends over 

 about one-third the body length. There is no trace of longitudinal marking on 

 the cuticle {vide PI. xxxiii., Figs. 1 and 2). 



The genital bursa or expansion at the tail of the male is well formed, and opens 

 by an oval opening with its long axis longitudinal. The bursa is supported by a 

 number of ridges as an umbrella is by its ribs, and, using Looss's nomenclature, 

 these are arranged in three groups. The members of each group arise from a 

 common root and are recognisable, even when, as in the case of T. pergracilis, 

 some of them run close to and parallel with members of another group. The 

 three groups are: (1) Dorsal; (2) Lateral ; (3) Ventral. 



The spicules in the male are very conspicuous and very difificult to describe. They 

 are short, strongly chitinised, with thickened edges and a kind of haft or base at 

 the anterior end ; and each spicule is hollowed something like a crumpled, withered, 

 lanceolate leaf. Each spicule is provided with retractor and protractor muscles, 



' Vide vol. ii. Appendix D. 

 VOL. I. 



