144 ANATOMY. 



112. 



THE SALIVARY VESSELS. 



Cuvier says, in his " Comparative Anatomy," that the secretory 

 organs of insects always assume a tubular form, and that consequently 

 conglomerate glands are wholly wanting in them. This assertion is 

 strictly true with respect to the biliary vessels, which have been con- 

 sidered as analogous to the liver, but in the salivary vessels we find 

 exceptions, and which are most strongly exemplified in the testes, some 

 of which (the epidydimis in Hyrdophilns) possessing many accumulated 

 acini. Nevertheless, the form considered by Cuvier as universal is cer- 

 tainly the most general. 



Under the name of salivary vessels we comprehend those glandular 

 appendages of the nutrimental canal which evacuate themselves either 

 into the mouth or into the commencement of the intestine in front of 

 the stomach, and by their secretion promote the digestion of the food. 

 The following are their chief differences : 



A. Salivary vessels which open into the mouth, generally beneath 

 the tongue, and more seldom at the base of the mandibles. They 

 take the following forms: 



1. As simple, long, undivided, twisted tubes ; thus in the ma- 



jority of insects, viz., all butterflies, many beetles and flies. 



2. As a narrow vessel which empties itself into one or two blad- 



ders, whence the salivary duct originates (Nepa, PI. XXII. 

 f. 1 ; Cimex, PI. XX. f. 3. A, A; Sarcophaga). 



3. As a ramose vessel with blind branches, (Blaps, PI. XXII. 



f.3). 



4. As two long, cylindrical pipes, which unite into one evacu- 



ating duct (Reduvius, PI. XXI. f. 15). 



5. As four small, round bladders, each pair of which have a 



common duct (Pulex, PI. XXI. f. 16; Lygceus, Cimex). 



6. As a multitude of such vesicles in Nepa (PI. XXII. f. 2). 



7. As capitate tubes, in the free ends of which many very fine 



vessels empty themselves (Tabanus, PI. XXII. f. 4). 



8. As tubes which at intervals are surrounded by twirling blind 



bags (Cicada, PI. XXII. f. 5). 



9. As granulated glands which on each side unite into a salivary 



duct, both of which join into a single evacuating duct (Gryl- 



