130 PEACTICAL PARASITOLOGY 



system, which, with the exception of the bladder, is usually empty and 

 for that reason indistinguishable, will now fill and will be clearly seen. 



Six Distomes and one Amphistome are found in the intestine of 

 our native frogs and toads. The Amphistome inhabits the terminal 

 portion of the gut, and is distinguished from the Distomes by its 

 sucker, which is placed at the hinder end of the somewhat barrel- 

 shaped body. The sucking organ of the Distomes, on the other hand, 

 is placed in the middle line upon the ventral surface of the body, 

 and has no relationship whatever to the excretory system. The 

 Amphistome is Diplodiscus subclavatus. 



The six Distomes inhabit the small intestines, and of these one, 

 Distomum turgidum = Brandesia turgida, lives within the intestinal 

 wall at the commencement of the duodenum. It is enclosed in a 

 cyst nearly as large as a pea, which projects beyond the outer surface 

 of the bowel-wall, and from which the parasite must be removed for 

 the purpose of examination. The five other varieties lie upon the 

 intestinal mucosa and are somewhat difficult of detection, on account 

 of their transparency and their small size. They should be sought 

 with a magnifying glass among the folds of the mucosa ; or the 

 mucosa may be scraped off, diluted with normal saline, spread out 

 upon a glass slide, and examined under a low-power microscope. 

 The parasites will be recognized by their movements, and may be 

 picked out with the spatula and put upon glass-slides. 



These five Distomidse are distinguished from one another by the 

 position of the genital opening. In two varieties it is placed in 

 the middle of the ventral surface, just in front of the sucker; in 

 the other three it is situated at the margin of the body. The 

 stomach-tubes will be seen to vary in length, and they may be either 

 long or short in species of either group. When "long" they will 

 extend backwards for a considerable distance beyond the ventral 

 sucker. The parasite which has the genital opening upon the ventral 

 surface of the body, together with short stomach-tubes which do not 

 reach as far as the ventral sucker, is Brachycoelium crassicolle Dis- 

 tomum crassicolle (fig. 52) ; while that with long stomach-tubes is 

 D. endolobum = Opisthioglyphe endoloba (fig. 53). The two species, 

 which are now recognized as belonging to separate families, differ 

 from one another in certain other respects. The testes, in crassicolle, 

 are placed symmetrically at the margin of the body close behind the 

 ventral sucker, while in endoloba, they are placed one behind the 

 other in the middle of the body and at some distance from the 



Ha2)lometra, and two species of the genus Pneumoneces (Pneumoneces variegatus 

 and P. similis). In addition to the Polystomide already mentioned, the urinary 

 bladder frequently harbours Distomum cygnoides, now called Gorgodera cygnoides 

 and Gorgoderina vitelliloba, though this is of rarer occurrence. 



