NERVOUS SYSTEM OF GRASSHOPPER — SCHMITT 



315 



A study of the positions of the attachments of the muscles inner- 

 vated by the second and third root nerves, however, shows an interest- 

 ing distribution. In general, it may be said that nerves from the 

 second root innervate muscles in the anterior part of the mesothorax, 

 and that nerves from the third root, exclusive of those concerned 

 strictly with intrinsic leg musculature, innervate muscles in the pos- 



Table I. — Mcsothoracic muscles of Dissosteira innervated by the second 



root nerves 



Sym- 

 Muscle bol 



Tergosternals C 



Do C 



Basalar epipleurals 

 (pronator-extensor 

 of the wing) E 



Do E 



Tergal promotor of 

 the coxa I 



Sternal promotor (an- 

 terior rotator of the 

 coxa) K 



Pleurocoxals (abduc- 

 tors of the coxa) . . . M 



Do 

 Do 



M 

 M 



Snodgrass 

 number 



83 



94 



95 

 96 



Origin 

 (or attachment) 



Posterior part of lat- 

 eral prescutal lobe 

 Scutum 



Insertion 

 (or attachment) 



Anterior part of 

 mesosternum 



Mesosternum be- 

 fore coxal cavity 



97 First basalar plate Lateral part of ster- 



num before base 

 of leg 



98 First basalar plate Anterior part of 



coxa 



89 Scutum 



92 Sternellum 



Anterior ventral 

 episternum 

 Do 

 Episternum 



Anterior angle of 

 coxa 



Anterior angle of 

 coxa 



Anterior outer mar- 

 gin of the coxa 

 Do 



Lateral margin of 

 the coxa, anterior 

 to pleural articu- 

 lation 



terior part of the segment. The depressor of the trochanter is an 

 exception and will be discussed later. Tables i and 2, based on 

 muscle descriptions given by Snodgrass (1929), show the various 

 muscle positions. 



A corresponding arrangement of nerves and muscles exists in the 

 metathorax. In the prothorax, the third root nerves innervate the 

 posterior group of muscles as in the pterothorax, but the second root 

 nerves are largely involved in musculature peculiar to the prothorax 

 and will accordingly be considered separately. 



