PHYSIOLOGY OF DIGESTION IN BLATTIDAE 363 
Between the main teeth are secondary and tertiary ones. 
These, unlike the primary ones, are covered with short spines. 
Between each pair of large teeth are three secondary ones, evenly 
spaced (fig. 9). Between each primary tooth and its adjacent 
secondary tooth are three or five tertiary teeth, and between 
adjacent secondary teeth are two or three tertiary ones. So 
the gizzard has six primary teeth, eighteen secondary ones, and 
sixty or ninety-six tertiary ones. 
The teeth extend through about half the length of the anterior 
gizzard.. The region between their posterior ends and the pas- 
sage from the gizzard into the stomach is provided with smaller 
rounded projections which are set with long yellow spines or 
needles. Just behind the primary teeth are considerable folds, 
which Miall and Denny have called cushions for the teeth. These 
are shown in figures 8 and 9. The spines here are large and uni- 
form, and are situated in sockets on the summits of dome-shaped 
chitinous projections. The structure and relations here will be 
discussed later. Posterior to the cushions les a region of many 
smaller lobes and folds, the walls of which merge into the duct 
leading to the stomach. ‘These lobes are thickly set with simply- 
structured bristles. Adjacent and opposite lobes are usually 
closely opposed to each other, so that little or no passage is left 
(figs. 8 and 15). They may thus effectually block the passage 
of food from the crop through the gizzard to the stomach. 
The epithelium of the anterior part of the gizzard merges into 
that of the posterior. This posterior part projects far into the 
stomach and consists of one epithelial layer bounding the lumen 
and another which turns back from the apex of the projection 
parallel with the first and outside of it. This epithelium merges 
with the extreme anterior end of the stomach wall, in the region 
where the coeca originate. The lumen of the projecting part 
of the gizzard is small and is almost obliterated, being reduced 
to a star shape by the projecting rounded folds of epithelium, 
which are surrounded by muscles. Occasionally I have found 
small black bodies in the cells here in preparations fixed in 
Flemming. The epithelium of the outer side bears small rounded 
chitinous bodies to which short spines are attached. 
