teeth 



THE PROVENTRICULUS 309 



teeth are triangular, sharp-pointed, and directed posteriorly, and gradually 

 decrease in size in succession from before backward. Each tooth is very 

 strong, sharp-pointed, and of the color and consistence of tortoise shell, and is 

 armed on each side by a smaller pointed tooth. These form the six longitudinal 

 ridges of the gizzard, between each two of which there are two other rows of 

 very minute teeth of a triangular form, somewhat resembling the larger one in 

 structure, occupying the channels between the ridges. The muscular portion of 

 the gizzard is equally interesting. It is not merely formed of transverse and 

 longitudinal fibres, but sends from its inner surface into the cavity of each of 

 the large teeth other minute but powerful muscles, a pair of which are inserted 

 into each tooth. The number of teeth in the gizzard amounts to 270, which is 

 the same number in these Gryllidse as found formerly by Dr. Kidd in the mole- 

 cricket. Of the different kinds of teeth there are as follows : 72 large treble 

 teeth, 24 flat quadrate teeth, 30 small single-hooked teeth, and 12 rows of small 

 triangular teeth, each row being formed of 12 teeth. This is the complicated 

 gizzard of the higher Orthoptera." (Newport.) 



In the more generalized cockroach, there are six principal folds, the so-called 

 teeth, which project so far inwards as to nearly meet (Fig. 312). The entire 

 apparatus of muscles and teeth is, as Miall and Denny state, ' ' an elaborate 

 machine for squeezing and straining the food, and recalls the gastric mill and 

 pyloric strainer of the crayfish. The powerful annular muscles approximate 

 the teeth and folds, closing the passage, while small longitudinal muscles, which 

 can be traced from the chitinous teeth to the cushions, appear to retract these 

 last, and open a passage for the food." 



As in the fore-stomach or proventriculus of the lobster, the solid, 

 rounded teeth do not appear to triturate the solid fragments found 

 in the organ, but act rather as a pyloric strainer to keep such bodies 

 out of the chylific stomach. We accept the view of Plateau that this 

 section of the digestive canal in insects, which he compares to the 

 psalterium of a ruminant, is a strainer rather than a masticatory stom- 

 ach, and both Forel and Emery, as well as Cheshire, take this view. 



The proventriculus of the honey-bee (Fig. 313, hs) is called by 

 apiarians the "honey-sac" or "honey-stomach." Cheshire states 

 that if it be carefully removed from a freshly killed bee, its calyx- 

 like "stomach-mouth" may be seen to gape open and shut with a 

 rapid snapping movement. The entrance to the stomach is guarded 

 by four valves, each of which is strongly chitinous within, and 

 fringed along its edge with downward-pointing fine stiff bristles. 

 By the contraction of the longitudinal muscles (lm), the valves open 

 to allow the passage of food from the honey-sac to the "chyle- 

 stomach." It is closed at will by circular muscles (tin). Then the 

 bee can carry food for a week's necessities, either using it rapidly in 

 the production of wax, or eking it out if the weather is unfavorable 

 for the gathering of a new store. 



Cheshire also shows that when bees suck up from composite and other 

 flowers nectar together with much pollen, the outside wrinkled membrane (s?n, 



