THE ANATOMY OF PENTASTOMUM TERETIUSCULUM. 17 



at the anterior end of the groove surrounding the papilla and 

 by the two plates just described, two well-developed muscle- 

 bands pass forwards, one on either side of the median line, to 

 be inserted into the body-wall at the anterior end of the head. 

 The joint action of the three sets of muscles — viz. (1) those of 

 the papilla, (2) those from the pharynx-wall, and (3) those 

 running forwards to the anterior end of the head — necessarily 

 results in a widening of the mouth opening of the pharyngeal 

 tube, whereby a sucking action will be produced and fluid 

 material passed upwards. Not only this, but the surface of 

 the papilla is marked by little rugosities, as is also the cuticle 

 lining the posterior surface of the mouth opening. The fan- 

 shaped mass of muscles within the papilla (fig. 32, M 5) is so 

 arranged that, together with the action of the muscles running 

 forwards into the head, the papilla must be rendered capable of 

 at least an up-and-down scraping movement, by which the 

 parasite is probably able to pierce the walls of blood-vessels in 

 the lung of its host. 



(2) Pharynx (fig. 32). — This leads directly upwards from 

 the mouth, and after running a short distance turns somewhat 

 abruptly backwards. It may be easily distinguished from the 

 oesophagus, into which it opens. 



In P. proboscideum,^ according to Stiles, the cuticle 

 lining the pharynx is thicker and stains more readily than 

 that of the oesophagus. On the anterior wall of P. tereti- 

 u senium, as seen in longitudinal section, the cuticle is thin, 

 except immediately opposite to a thick cushion-like pad in the 

 posterior wall to be soon described. On the posterior wall it 

 becomes considerably modified. The layer becomes much 

 thickened in the lower half of the pharynx, and a special 

 portion can be clearly seen as represented in fig. 32. This has 

 the appearance in longitudinal section of a tooth with its 

 pointed end lying close to the mouth. The surface facing into 

 the pharynx bears distinct rugosities, and the upper end 

 appears to have a definite relationship to a curious swollen 

 portion of the wall of the pharynx just where it turns sharply 

 » Loc. cit., p. 123, Taf. viii, fig. 4G. 



VOL. XXXlVj PAET I. NEW SEK. B 



