PHYSIOLOGY OF DIGESTION IN BLATTIDAE 381 
region is practically always open for the passage of food. The 
appearances are much clearer if studied in longitudinal sections; 
such sections were evidently not used by most investigators. 
For the study of the intimate structure of the cushions great 
care. in preservation and the changing of reagents is necessary. 
Flemming’s fluid often causes a loosening of the intima and the 
destruction of its structure. Any preserving fluid may do this, 
or insufficient dehydration, or too rapid passage into paraffin. 
Only after many trials was I able to demonstrate the fibrillar 
structures leading to the needles as Petrunkevitch has described 
them. I believe that the other investigators took insufficient 
precautions with the material, thus destroying the intimate 
structure. Flemming’s fluid is satisfactory if the material is 
left in it two days; Perenyi’s fluid may also be used. It is 
necessary to use iron haematoxylin as a stain, followed by picro- 
fuchsin. Even then many preparations do not show the desired 
structure, for the fibrils and their connections are to be seen 
only in a limited area, and it is only by chance that sections can 
be made in just the right plane. In well-preserved preparations 
it is clearly seen that the muscles of the muscle band divide to 
fibrils (fig. 11) which pass between the epithelial cells and be- 
come little tendons. The tendons traverse the modified intima 
to attach to the socketed bases of the needles. 
The muscle bands are six in number, and run from the intima 
of the cushions outward and upward to their origin in the thick 
and comparatively immovable chitin of the anterior surface of 
the teeth. The muscles are long and well striated; their con- 
traction can cause little movement at their origins, so it must 
result in movements at the insertions in the cushions. The 
insertions are in the bases of the needle, and the sockets seem 
to allow them to move in response to muscular pull. Thus the 
structure certainly indicates that the muscles move the needles. 
A cross-sectional view of the muscle tendons which traverse 
the intima may be seen in sections cut nearly parallel to the sur- 
face of the intima, and just below its surface. Figure 12 shows 
such a picture: the tendons are seen within the matrix of the 
intima in the region between the epithelial cells and the surface 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, NO. 2 
