208 My Harrison, A preliminary account of the 
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the matter up finally. His account, though an advance on any 
previously published, fails in several important respects. Patton — 
and Cragg (1913) have also described the mouth-parts of Pediculus, — 
but, although they have given a more correct account of the — 
structure of the piercing apparatus, their description of the buccal — 
eavity and pharynx, and more especially of the musculature, falls 
behind that of Pawlowsky. The paper of the latter gives an_ 
excellent summary of the history of the controversy, from Sa 
merdam to the date of his own paper. 
Material and Methods. 
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This paper sets out part of the results of an enquiry into the | 
structure and bionomics of Pediculus which was undertaken by | 
the staff of the Quick Laboratory at the instance of the Medical 
Department of the Local Government Board. As it is largely 
concerned with an interpretation that is of academic rather than : 
practical interest, I take this opportunity of publishing my inter- — 
pretation somewhat fully, so that I need not encumber an official ~ 
report with more than a summary of it. Material has been | 
furnished by various medical officers in the service of the Board, 
and was also obtained at the Ist Eastern General Hospital, from 
the clothing of wounded soldiers. This material was fixed in 
Carnoy’s fluid. For the preparation of satisfactory.sections I have 
to thank Dr Keilin, of the Quick Laboratory, who placed his very 
considerable technical experience entirely at my service, and 
developed a technique suitable for dealing with this difficult 
material. No reagent was used to soften the chitin, as experience 
with Mallophaga had shown me that the use of strong reagents, 
such as Hau de Labbaraque, is not altogether satisfactory. The 
difficulty of securing satisfactory infiltration was finally overcome 
by embedding im vacuo, and sections were cut at 64, and stained 
in Mann’s stain. In addition to longitudinal and_ transverse 
sections of the head, dissections, with and without the use of 
potash, were made, both of Pediculus and of the larger Anopluran 
species, Haematopinus tuberculatus and H. suis. Freshly killed 
insects cleared in glycerine also proved useful; while, for the 
structure of the chitinous parts, moulted skins of the larvae were 
supremely useful, as a beautiful cast of these parts can thus be 
obtained. 
General Relations. 
The stomatodaeum of Pediculus is divisible into four distinct 
portions, a buccal cavity, pumping-pharynx, pharyne proper, and 
oesophagus. The buccal cavity is an approximately cylindrical 
tube, leading horizontally from the terminal mouth opening to the 
pumping-pharyna. It is‘13 mm. in length, and is wider posteriorly 
