LIFE HISTORY 29 



remains near the top of a milk jug. They constantly 

 apply their 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. i6. — A diagrammatic figure of the alimentary canal of the 



liouse fly ; greatly enlarged. Ph., Pharynx ; Oes., Esophagus ; 



P. Ven., Proventriculus ; Ven., 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 



