THE Hoc Louse | 687 
appeared like a cross as it is figured in the man-infesting louse by the 
different investigators. The tissue of the pharynx wall isin parts very much 
developed, but its precise histological nature has not been determined. 
Neither in appearance nor in staining reaction does it correspond to a 
simple epithelium. Where the wall of the pharynx is strongly chitinized, 
both the muscle and the epithelium are thin (Plate LXI, 9), but in the 
region between the second area of chitinization and the transition to the 
slender esophagus the wall is so thick that the lumen is reduced at rest 
almost to a slender transverse slit (Plate LXI, 1). 
The salivary glands 
Since the time of Landois (1864:9) it has been known that lice possess 
two pairs of salivary glands situated in the thorax. It was Pawlowsky 
(1906 : 199-200), however, who first described the glands opening into the 
piercer sheath, and his name has been given to these glands by subsequent 
workers. Still more recently a fourth gland, situated between the rami 
of the piercers, has been described. 
Pawlowsky’s glands are simple tubular glands lying on either side of 
the piercer sheath, into which they open through wide conduits at the 
level of the eyes (Plate LXII, 1). They have at this point a depth of 0.1 
millimeter and a width of 0.05 millimeter, while their length is approxi- 
mately 0.33 millimeter. They rest on the tendon of the dorsal lateral 
retractor muscle of the piercer sheath, and this causes an oblique indenta- 
tion in their posterior ventral’ surface. They have a lining of epithelial 
cells which are not clearly defined from one another and which show the 
usual reactions to stains. Pawlowsky (1906:200) suggests that their 
secretion may serve to irritate the wound or to lubricate the piercing 
organs, but Harrison (1916b:217) has seen no sign of glandular activity 
and suggests that they are functionless. No secretion has been found 
in the lumina of the glands in any of the sections studied, but in a rather 
oblique longitudinal section there is some appearance of activity of the 
cells. This, however, may be due to the fact that the section is rather 
close to the lateral wall of the gland (Plate LXII, 2). 
Between the rami of the piercers lies an unpaired gland (Plate LX, 5 
and 6), which was first seen by Sikora (1916:54) in Pediculus vestimenti 
and was called by her the “ Stacheldriise.” It is somewhat wedge- 
shaped, being broadest at the anterior end, is clothed with cylindrical 
