G. H. F. Nuttall 
315 
teeth which are directed outwardly (compare Text-figs. 6 and 7). The 
greater number of these teeth (Text-fig. 8) are semicircular in obntour, 
these measure about lOp. in width, but at the fundus of the vagina they 
are long and pointed, measuring about 10 fj, in length; the distribution of 
the two kinds of teeth is sharply defined as shown in the accompanying 
illustrations (Text-figs. 7, 8). Laterally, chitinous ligaments (ligts.) 
running to the exoskeleton at the intersegmental folds, serve to hold 
the vagina in place. The vagina at its fundus leads into the uterus 
Fig. 8. Pediculus humanus $. Detail showing the dentition of the vaginal wall where 
the shape of the teeth changes abruptly a.s indicated likewise in Fig. 6. The pointed 
teeth measure 10/r in length. 
(Text-fig. 7, Vt.) whose deUcate and structureless chitinous lining is 
thrown into numerous deep convoluted folds allowing of great expansion 
for the passage of the eggs. The uterus is provided with a powerful 
musculature consisting, as Landois first showed, of transverse and oblique 
muscles surrounding its lumen (Text-fig. 6, M. constr. id.); a consideration 
of the uterus does not, however, enter into the province of this paper. 
The structures above enumerated can be seen to a great extent in 
living specimens, the teeth covering a part of the vaginal wall being 
visible also by transparency. Text-fig. 7 was drawn from a specimen 
Parasitology i .x 21 
