1952 ] Eisner and Wilson — Formicine Proventriculus 55 
a note in passing. The wall consists of a loose aggregation 
of epithelial cells with variably polyploid nuclei. Our 
method of fixation (Schaudinn’s, five minutes) shows a 
dense concentration of basophilic granules in the cytoplasm. 
The cells themselves are so loosely connected that they can 
be dissected out individually with a fine pin, and it seems 
unlikely that they are able to withstand much pressure 
from the contents of the lumen. 
It has been generally understood that the proventriculus 
functions in some way to allow storage of liquid in the 
crop and to regulate the amount which passes into the 
midgut. This increase in efficiency at storing food in turn 
facilitates a greater rate of trophallaxjis, which is a 
fundamental bond of social life in higher ants. As to the 
specific mode of action of this organ, Emery proposed a 
scheme in his original paper (1888) which to the present 
time has been varied upon only slightly. This scheme can 
be summarized as follows. The occlusory tract acts as a 
valve which is controlled by the muscles surrounding it and 
which is able to seal off completely the bulb from the crop. 
In the euformicines the calyx acts as an accessory valve, 
collapsing its walls together to prevent the flow of liquid 
through it. The bulb acts as a unidirectional pump with a 
valve on each end. As the transverse muscles contract, 
the adjacent walls of the bulb collapse on one another, first 
at the periphery and then toward the center, forcing the 
contents of the cavity down through the cylinder and into 
the midgut. At the same time the occlusory tract closes 
off independently and prevents flow of the bulb’s contents 
forward into the crop. As the bulb muscles relax, the 
elasticity of the chitinous wall opens the cavity and creates 
suction, while the occlusory tract opens and allows liquid 
from the crop to fill the bulb. The ‘‘knob”, the end of the 
cylinder which enters the midgut cavity, acts as a valve to 
prevent flow of liquid back from the midgut, since its 
cavity is collapsed by slight external pressure. Regurgita- 
tion is initiated by a closure of the occlusory tract (and 
calyx also in the euformicines) and an expansion of the 
pharyngeal cavity; the latter process sucks liquid forward 
out of the crop. This original scheme was based entirely 
on prepared, sectioned material. 
