CH. Ill] 



THE COCKROACH 



81 



as a favour from sailors by native tribes, who are greatly 

 troubled with those parasites. The strong teeth at the 

 tips of the mandibles and the roughened grinding surfaces 

 near the base of their inner edges fit more or less closely 

 into one another right and left, and appear not only to bite 

 off pieces of food but also to grind them into fragments 

 sufficiently small to pass along the narrow gullet into 

 the large crop. Prior to being swallowed, the food is 

 moistened by the faintly alkaline secretion of the salivary 

 glands, which not only lubricates and softens but is also an 

 actively digestive fluid capable of converting starch into 

 sugar. Further digestion is brought about in the crop into 

 which there passes forward the feebly acid secretion of the 

 seven or eight hepatic ("liver") tubes which are connected 

 with the chylific stomach at its anterior end close behind 



Fig. 17. Mouth- appendages of Periplaneta. Magnified. 

 Mandible. B. 1st maxilla. 1. Cardo. 2. Stipes. 3. Lacinia. 

 4. Galea. 5. Palp. C. Eight and left 2nd maxillaj fused to 



form the labium. 1. Submentum. 2. Mentum. 3. Ligula, 

 corresponding to the lacinia. 4. Paraglossa, corresponding to the 

 galea. 5. Palp. 



L. 



6 



