102 M. O. Strobelt on the Anatomy and 



they approximate the upper to the lower integument, and thus 

 assist in respiration, as will be explained further on. Lastly, 

 we find two more muscles on each side, which, commencing 

 far back on the dorsal surface of the head, run forwar 

 (fig. 4, V b), one of them nearly parallel to the middle line 

 (&'), the other more towards the ventral surface (b). Upon 

 the last-mentioned pair the cerebral ganglion rests. As to the 

 function of these two pairs of muscles I can say nothing with 

 certainty ; but I suppose that they also assist in respiration. 



Musculature of the Thorax. — The muscles of the thorax 

 may also be divided into three groups — the muscles of the legs', 

 the muscles which serve for the constriction of the thorax, 

 and the motors of the head. 



Muscles of the Legs. — These muscles are all attached to the 

 chitinous pad, already repeatedly mentioned, which originates 

 in the middle of the posterior margin of the dorsal surface of 

 the thorax, runs forward in the direction of the median line, 

 then divides and runs towards the anterior angles of the thorax 

 (fig. 4, 1). These muscles penetrate into each leg. Those 

 going to the first pair originate a little before the point where the 

 above-mentioned chitinous band forks, form with this an angle 

 of about 45°, and are inserted upon the anterior and posterior 

 margins of the base of the coxa ; these move the legs forward 

 and backward (fig. 4, v'). Immediately behind these the 

 forward and backward motors of the succeeding pairs of legs 

 take their origin, starting from the chitinous band nearly at 

 a right angle (fig. 4, m f & h 1 ). The musculature is exactly 

 the same in all three pairs of legs, except that the muscles ol 

 the first pair are much more delicate than those of the two 

 posterior pairs, as the legs of the first pair are far less powerful 

 than the others. At the base of the coxa originate four 

 muscles which converge forwards, and are inserted upon the 

 lower margin of the trochanter (fig. 6, c) . The short trochanter 

 exhibits only two muscles, which are tolerably broad at the 

 posterior end, but become considerably narrowed anteriorly 

 and run divergently. They have their origin at the base of 

 the trochanter, and terminate at the lower margin of the femur 

 (fig. 6, tr). The musculature of the femur is of a somewhat 

 different type. One muscle traverses the femur from behind 

 forwards, parallel to the long axis of the leg. Two pairs are 

 inserted on each side at some height on the posterior margin 

 of the femur, and run obliquely through it to the anterior 

 margin of the basal part of the tibia (fig. 6/). The three 

 muscles just mentioned are flexors of the tibia. Besides these 

 the femur shows two more muscles, which are inserted on each 

 side above those last named, penetrate into the tibia, and then 







