LIFE HISTORY 
29 
remains near the top of a milk jug. They constantly 
apply ttieir mouth parts to the surface over which they 
are walking, attempting to suck up some nutrition, 
and under certain conditions the imprints of their oral 
lobes can afterwards be made out under the lens. 
In order to understand the digestive processes of a 
fly and to comprehend fully just what a disease germ 
Fig. 16.—A diagrammatic figure of the alimentary canal of the 
house fly ; greatly enlarged. Pit., Pharynx ; Oes., Esophagus; 
P. Ven., Proventriculus; Veil., Stomach; F. Int., Fore 
intestine; H. Int., Hind Intestine; Cr., Crop; 
Rect., Rectum. 
passes through after it is sucked up by one of these 
creatures, it is necessary to know something of the 
structure of the alimentary canal. This is simpler with 
the house fly than with many other flies, more so in 
fact than that of the blow fly, whose anatomy was so 
carefully worked out by the famous English micro- 
scopist, Lowne. It consists of a pharynx, a rather 
narrow esophagus, a proventriculus or chyle stomach, 
a crop, a ventriculus or true stomach, a fore and a hind 
