50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



are the lateral dilator muscles. Others lie beneath the ventral longi- 

 tudinal dilators and function in a similar fashion to those muscles. 

 Since these small sheets of muscles have the same apparent function 

 as the larger muscles with similar insertions that are adjacent to them, 

 they are not assigned separate numbers in this list. 



THE SALIVARY GLANDS 



A dissection in which the alimentary canal is removed and the 

 mouth and preoral cavity are arranged so that one, in examining the 

 preparation, looks out the mouth opening (fig. 3 A), reveals not only 

 the musculature of the oral lobes very clearly, but also indicates that 

 the salivary ducts are formed into a series of complicated folds that 

 form very effective valves. Each salivary gland empties into a but- 

 ton-shaped chamber (iB) lying laterad of the ventral longitudinal 

 sheet of muscles (vld). The common salivary duct (Sd) lying be- 

 tween these chambers is connected to each chamber by narrow bands 

 of muscles, each band fanning out distally where it inserts on the 

 chamber (Icsp). 



When the ventral longitudinal sheets of muscles are removed, a 

 second swelling in each lateral duct is revealed lying mesad and 

 slightly underneath the first chamber (figs. 3 B, C, 2 B). These 

 chambers form not only an effective salivary pump but also the valves 

 that are so necessary in the operation of such a pump. 



The muscles that operate the pump and valves are as follows : 



9. The paired lateral compressors of the salivary pump originating 

 on the walls of the median salivary duct ; inserted on the outer cham- 

 ber (fig. 3 A, B, Icsp). These muscles by their contraction close the 

 valve between the pump and the salivary gland when the salivary juice 

 is being ejected from the common duct into the preoral cavity. 



10. The median compressors of the salivary pump. A pair of longi- 

 tudinal muscles lying near the center line originating on the body 

 wall and inserted on the inner edge of the inner chamber of the pump 

 (fig. 3 B, C, mcsp). These muscles when contracted prevent a twist- 

 ing movement of the lateral ducts, thus aiding in the closing of the 

 passage between the two chambers. 



The compressor muscles are opposed in their action by several small 

 muscles that, when they contract, together open the passage between 

 the two chambers. They are : 



11. The lateral extensors of the salivary pump. Each muscle of this 

 pair is attached distally to the body wall and medially to the inner 

 edge of the outer chamber (fig. 3 C, lexsp). 



