NERVOUS SYSTEM OF GRASSHOPPER — SCHMITT 309 



The illustration of nerves and muscles for the purpose of showing 

 patterns and relationships also presents a problem. Realistic figures 

 may show clearly the precise manner in which nerves pass among 

 muscles, but when such figures deal with complex nerve-muscle sys- 

 tems, they often fail to reveal the entire segmental pattern or the rela- 

 tionships believed to provide points of homology. In this paper, an 

 attempt is made to serve these objectives by the use of diagrams which 

 indicate the spatial relationships of the nerves but which substitute 

 numbers for the muscles innervated. The termination of a nerve on 

 the integument is indicated by a short line drawn across the nerve. 



I. GENERAL DESCRIPTION 



A dorsal view of the cervicothoracic nerve cord of Dissosteira is 

 shown in figure I. The posterior portion of the suboesophageal 

 ganglion usually may be seen projecting slightly from beneath the 

 tentorial bridge. Two fine nerves, the cervical nerves, leave the sub- 

 oesophageal ganglion posterior-laterally and pass dorsally, generally 

 close to the postocciputal ridge. 



The paired interganglionic connectives from the suboesophageal 

 ganglion pass beneath the crossed prosternal muscles of the cervical 

 sclerites (54) to the prothoracic ganglion. This ganglion lies in a 

 pocket provided by the anterior prosternal plate or basisternum, be- 

 tween the sternal apophyses and immediately anterior to the pro- 

 thoracic spina. Connectives from the prothoracic to the mesothoracic 

 ganglia pass beneath the sternospinal muscles (61), the second pos- 

 terior rotators of the prothoracic coxae (67), and the third ventral 

 longitudinal muscles (87), and lie parallel with and just beneath the 

 fourth ventral longitudinal muscles (88). The mesothoracic ganglion, 

 like the prothoracic, is located above the basisternum of its segment, 

 between the sternal apophyses and anterior to the mesothoracic spina. 

 The fourth ventral longitudinal muscles (88) thus pass just above the 

 mesothoracic ganglion. A pair of fine nerves leaves the dorsal surface 

 of the mesothoracic ganglion and passes to the salivary glands. The 

 definitive metathoracic ganglion lies immediately posterior to the 

 spina and is connected to the mesothoracic ganglion by short con- 

 nectives which lie on either side of the spina. The anterior rotators 

 of the mesothoracic coxae (93) and the sixth ventral longitudinal 

 muscles (117), pass immediately above the definitive metathoracic 

 ganglion to their origins on the mesothoracic spina. The ventral 

 nerve cord may thus be seen to occupy a very definitive positional 

 relationship with the ventral skeletal elements of the thorax in Dis- 



