366 ANIMAL PARASITES. 



In Oxyuris vermicularis I have not yet found this orifice ; but 

 it is very probable that I have overlooked it. With regard to 

 the four lateral cords see also Ascaris lumbricoides. 



The alimentary apparatus consists of the following parts : 



The mouth, reaching to the apex of the head, which is rendered 

 very broad here by the wing-like appendages, is on the whole 

 narrow and very muscular. In the Oxyuris ornata it terminates 

 anteriorly with four ridges (Wiilsten) of corium, in which a nervous 

 dilatation, broad in front, pointed ^behind (a sort of tactile organ), 

 is observed. Wedl mentioned three, or perhaps four, retractile 

 papillae in Oxyuris vermicularis ; these are nothing but Walter's 

 ridges of corium. The conditions which prevail in O. vermicu- 

 laris are not very easily reviewed ; but in this case also it is most 

 probable that we have to do with four ridges of corium, although 

 it may usually appear that there are only three such ridges. At 

 any rate the ridges are unequal, and whilst two of them each 

 measure about 0'025 0-028 mill., the other two ridges, which 

 cover each other, measure together about the same, which is cer- 

 tainly possible only if the ridges of corium (lips, papillae) differ 

 in size amongst themselves. The notches between the individual 

 ridges measure about O'OOIS mill, in the male, and twice as much 

 in the female. I asserted formerly that the number of ridges 

 (papillae) must be three, and upon this supported my assumption 

 of the triangular form of the oesophagus, but I have since seen, 

 from Walter's investigations, that this triangular form of the 

 oesophagus has nothing to do with the ridges of corium, as the 

 oesophagus does not reach to the mouth, and the pharynx is 

 round, and not composed of three pieces. 



Between the mouth, the breadth of which is about 0'039 mill., 

 and the oesophagus, there is a muscular pharynx (rich in annular 

 muscles), which increases in thickness posteriorly ; at the hinder 

 extremity of this there is a constriction, which corresponds with a 

 small intumescence in front. The skin of the pharynx in the 

 Oxyurides, according to Walther, is firm externally, structureless, 

 and without folds internally. Between the pharynx and the 

 cylindrical oesophagus there is a sort of diaphragm, a chitinous or 

 cartilaginous lamella. Towards the stomach a new constriction 

 occurs, which separates the oesophagus from the stomach. The 

 cavity of the oesophagus itself is prismatic and triangular, as far 

 as the stomach. The angles of this prism are formed by three 

 firm cartilaginous seams, which occur in the interior of the 



