112 
Mouthparts of Pediculus 
asymmetrical appearance to the stabber. When the stabber is isolated the 
double gouge shows a blade broader and thinner than the blades of the 
ventral stabber. Near the piercing end, the two elements become singly 
concave and bear a three-pointed tip, the centre point large and the flanking 
ones smaller, the whole recalling the appearance of the needle point of a 
syringe. I think that the salivary pipe becomes part of this point, as sections 
and dissections do not show any separation of salivary pipe and stabber. 
The above-mentioned spindle of tissue is of interest. It begins as an aggre¬ 
gation of a few cells attached to, and beneath, the roof of the postero-median 
portion of the sac just above the region of the bifurcation. These cells stain 
blue and their nuclei almost black. The spindle runs forward above and 
separates from the dorsal stabber, and certain sections show the presence of a 
lumen; it then traverses the elements of the dorsal stabber and runs forward 
whilst attached ventrally to them. The spindle carries attached beneath it 
a chitinous tube, the salivary pipe, and ceases about the end of the anterior 
third of the stabber. At its widest region, in cross-sections, it shows a reddish 
stained core which appears to consist of longitudinal muscle fibres surrounded 
by a layer of blue-stained cells. Anteriorly the tissue stains pink and contains 
two groups of blue-stained cells. The function of the tissue is considered later. 
Salivary Pipe. As already mentioned the salivary pipe is a chitinous tube 
of very fine bore running beneath the dorsal stabber tissue. As this tissue 
diminishes and ceases anteriorly the pipe is brought nearer to, and I think, is 
fused mid-ventrally to the elements of the upper stabber in the angle between 
them. A drawing made by Professor Nuttall and a dissection by Mr Lloyd of 
the posterior end of the pipe show a swelling in this region, and Harrison also 
pictures it. In my opinion Mr Lloyd’s dissection demonstrates that into this 
bulbous structure open the four salivary ducts. The function of the pipe is to 
lead the saliva into the wound. Its relationships with other structures are 
considered later. 
Ventral Stabber. According to my dissections and sections this stabber is 
composed of two similar elements, dorsal and ventral. Harrison does not show 
this. Each element closely resembles the dorsal stabber. 
The posterior rami of the dorsal element have a wider span than those of the 
dorsal stabber. They are somewhat bow-shaped, with two curves, and run 
forwards, externally to those of the upper stabber, and their convergence 
and fusion take place slightly behind and beneath the upper stabber’s broad 
region. Here the structure has a short, broad, shallow groove facing dorsally. 
Anteriorly again, the chitin flattens and tapers and the groove disappears. 
Next, in the piercing portion appear three dorsal longitudinal grooves (only 
one of which is represented in PI. VI, fig. 2), one median and two lateral. The 
median groove persists along the whole length of the stabber and lodges the 
salivary pipe, but the others become gradually less pronounced and, in the 
anterior fifth of the stabber, are scarcely recognisable. The edges are flanged. 
Harrison regards them as crenate but dissections and mounted preparations 
