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I "■ ' * ' ^ 
A. D. Peacock 
failed to grasp the true significance of the relationships of the mouth-parts. 
From the floor of the pumping-pharynx, slightly behind the region where the 
food canal and sac diverge and dorsal to the sac tube, the paired pharyngeal 
half-tubes (ph.t.) have their origin. These evidently compose Harrison’s 
“buccal tube.” These half-tubes by their apposition to one another form a 
suctorial pumping-pharyngeal tube (Text-fig. II) through which blood is drawn 
during feeding. Anteriorly they are embraced by the sac tube. As the 
ensheathing sac tube and the suctorial pumping-pharyngeal tube both lie 
in the buccal region it is suggested that the use of Harrison’s term “buccal 
tube” be discontinued. 
The two stabbers, when retracted, rest one above the other along the 
whole length of the sac. They are similar in so far that each resembles a 
Fig. II. Pediculus humanus. Mouth-parts in transverse section at the anterior part of the buccal 
region. The suctorial tube is situated dorsally to the stabbers and salivary pipe, the complex 
lying within the hollow of the sac tube. The suctorial and sac tubes are each composed of 
two elements. Slightly diagrammatic. 
4 
two-pronged fork with the rami pointing backwards (PI. VI, fig. 2). The 
stabbers are slightly curved and lie completely retracted within the head. In 
the buccal region they lie beneath the pumping-pharyngeal tube and are 
embraced by the sac tube. Their posterior rami are connected with muscles 
and the sides of the sac. Between the stabbers lies the salivary pipe, which, 
according to my sections, appears fused along its anterior length to the 
upper stabber. 
When the louse wishes to feed it would appear as if the parts must 
function as follows: the stabbers are extruded and thrust for about one-third 
of their length into the human skin. The buccal arch, pumping-pharynx 
and pharynx are brought forward, the haustellum is everted and the tips of 
the pumping-pharyngeal tube and sac tube touch the surface of the epidermis. 
