MECHANICAL PROTECTION AND POISONS 



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muscular apparatus has been found that could be used to inject the 

 venom. 



The Arachnids show a rather remarkable histological advance on the 

 usual insect types in regard to their poison glands. In place of the very 



FIG. 347. Slightly oblique section through the base of a poison hair of Sibine slimulea where it 

 leaves the skin, p.c., poison cell (a syncytium) with a hollow lumen to carry the poison 

 outward, hyp.c., hypodermal cells which make the hair cuticle. X 435. 



remarkable secreting cells, with the cuticle that lines the usual form of 

 insect poison gland, we find a gland whose secreting cells are naked dis- 

 tally and which possess no peculiar intracellular differentiations. 



The poison glands of the spider, Lycosa sp., form a good example. 

 These glands are integumental invaginations from the tips of the biting 

 mandibles, and they extend into the anterior part of the thorax. 



