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Psyche 
[December 
bar, however, belongs properly to the roof of the pump and 
will be described in detail later on. From this point the 
walls of the pump taper sharply, converging to form the 
entrance of the esophagus. 
From a lateral view (Plate 10, Fig. 2) the pump is ob- 
scured at its juncture with the cranium, by the presence 
of the bristle pouches, which must be cut away to permit 
adequate inspection of the structures. The cibarial portion 
of the pump expands gradually for approximately half of 
the entire length. Then it bends ventrally, forming the en- 
larged pharyngeal portion in which the sclerotized bar is 
again plainly visible through the wall. Directly behind the 
bar, the dorsal edge of the ventral wall detaches from the 
cranium and descends to form the entrance to the esopha- 
gus. The large pharyngeal dilator muscles emerge below 
the esophagus at this point and attach to the posterior wall 
of the cranium. 
If a head is placed on a block of paraffin with the dorsal 
side up and sectioned free hand along the midsagittal line 
with a very sharp blade, the two halves can be separated 
and examined under a stereoscopic microscope. If one half 
is placed in glycerin for a few hours, the tissues will par- 
tially clear showing the sclerotized structures in sharp 
relief. The other half preserved in alcohol will be better for 
the study of the muscles themselvs. Specimens fixed for a 
few hours in alcoholic Bouin’s solution were used in study- 
ing the frontal ganglion as the picric acid in this fixative 
stains the muscles darker than it does the nervous tissue. 
The structures as seen in such a dissection are shown in 
Plate 10, fig. 3. 
There are three discrete groups of muscles which oper- 
ate the food pump. The first group, which is distinctly 
cibarial in origin, operates the delicate anterior portion of 
the pump. These ntuscles arise on the striated inner sur- 
face of the cranium and insert by means of slender sclero- 
tized apodemes on the midline of the roof of the pump. 
The action of these muscles is obvious and direct. They 
raise the roof of the food channel and thus draw food from 
the stylets into the pump. This group of muscles, which 
will be referred to as “Group 1”, consists of the dilators 
