PHYSIOLOGY OF DIGESTION IN BLATTIDAE 379 
In my experiments I have never fed food consisting of large 
particles, so of course I have never observed any appearances of 
mastication. Food is almost never found between the points of 
the teeth. I have found considerable pieces of chitin in the 
lumen of the stomach; some small ones are shown in figure 19. 
These must represent relics of food which passed through the 
_ gizzard without being crushed much. I therefore agree with the 
majority of authors on the subject in not emphasizing the chew- 
ing action of the teeth. As the contour of the teeth may be 
such that they fit very compactly together, this part of the 
gizzard may act as a sphincter, though not as a perfectly tight 
one. Figure 8 shows the spaces which are usually present be- 
tween the teeth. It is not here that the main sphincter action 
of the gizzard resides. 
Food is found between the teeth and also in the regions of the 
secondary and tertiary teeth and other projections. The food 
is evidently guided from crop to gizzard by following in the 
narrow channels between the projections. The teeth must 
open somewhat to let the larger particles pass. The movement 
is peristalsis of the crop, which is often very powerful when ob- 
served in the living animal. 
As mentioned in the section on the crop, the gizzard is of 
importance in conducting forward the secretion from the stom- 
ach. For I have found an acid secretion in the hind crop be- 
hind ligations, and this seems to have flowed thence from the 
stomach. How the passage forward through the gizzard occurs 
has not been determined, but it seems probable that it flows in 
the narrow channels between the projections. These channels 
are the ones used later by the food in its passage backward. I 
have endeavored to demonstrate the forward passage of stom- 
ach secretion by injecting colored fluids into the stomach of 
the living animal. Such operations have always proved rapidly 
fatal. 
Ramme studied the flow of the secretion in various Orthop- 
tera, but not in the American cockroach. In some he found 
special passages which led from the origin of the coeca directly 
into the rear gizzard. I have studied serial sections of this 
