THE MUSCULAR SYSTEM. 261 



of three bellies, which pass like three rays from the pleura, and insert 

 themselves at the most posterior horny piece lying at the base of the 

 wing (the axillaire trolsieme of Straus). 



Besides which, small muscles support the bending back of the wing, 

 and which originate from the plate-shaped tendon of the large extensor, 

 inserting themselves at other horny plates at the base of the wing : 

 when in action they cause the relaxation of the extensors, and are 

 thence called relaxatores extensorum. 



179. 



MUSCLES OF THE LEGS. 



The motive apparatus of the legs is much more complicated, both 

 from their being so much more moveable, and from their consisting of 

 several consecutive joints. 



The coxas or hips receive the majority of muscles, but which are 

 adapted to the variations of their connection with the sternum. 



If they, as in the Coleoptera, consist of a cylinder revolving upon its 

 axis, the flexor of the fore legs are placed at the posterior margin of 

 their inner aperture, and the extensors at the anterior margin ; but in 

 the posterior pair, the latter are placed at the posterior margin, and 

 the former at their anterior. Both come from the lateral parts of the 

 notum, or from the internal processes of the sternum. In Melolontha, 

 Straus found in the fore legs, which, in all beetles, have the freest 

 motion, four extensors, which differed in size, and all came from the 

 posterior part of the pronotum, and but one flexor ; in the intermediate 

 pair, three flexors and two extensors, the longest of which came from 

 the margin of the prophragma. and the shortest from the internal pro- 

 cess of the sternum : the posterior coxse had, again, four extensors and 

 three flexors, some of which originated from the internal process of the 

 sternum, and the others from the dorsal and lateral plates. In the 

 water beetles,, the very large posterior coxa? are intimately connected 

 with the metasternum, and not articulated, from its receiving the 

 enormous muscles which move the remaining portion of the leg. The 

 muscles of the coxae are compressed by them, and the muscles which 

 move the leg pass from the internal process direct to the trochanter. 



Such coxae as are free do not differ in structure from those which 

 are received within a cavity of the sternum, with the exception, that 

 their aperture exactly corresponds with the aperture of the sternum. 



