PHYSIOLOGY OF INSECTS. 157 



touch, except in a few parts in which the nerves 

 obviously ramify to the surface. 



593. The organs of motion in insects are enclosed 

 within, and attached to, the organs of support ; 

 they are evident muscles, partly fleshy, partly ten- 

 dinous, and differ in no material character from 

 the muscles of vertebrated animals. 



594. The organs of sensation in insects are 

 distinctly and decidedly nerves, and in most 

 respects resemble the nerves of vertebrated ani- 

 mals ; they do not, however, originate in a com- 

 mon or concentrated brain, but in numerous 

 incrassated bundles of nerves, which are now 

 termed cerebroids. 



595. The usual animal senses are possessed 

 by insects ; most of them obviously. Of hearing, 

 we find slender proof, and its seat is altogether 

 unknown ; we also rather presume than know 

 that insects possess smell ; its seat is also un- 

 known. 



596. The organs of digestion in insects are 

 peculiarly simple : the alimentary canal is very 

 short, and the intestines generally without convo- 

 lutions ; the food passes very rapidly, and under- 

 goes but little alteration. 



597. The organs of circulation are these : a 

 longitudinal series of little hearts, now termed 

 corcula, of arteries, and of veins ; the blood is 

 transparent and colourless, it contains numerous 

 consistent oat-shaped particles ; it flows very 



