NERVOUS CONTROL OF INSECT MUSCLES 



79 



tractions under the nerve endings. Marcu (1929) counted the endings on 

 fibers of thoracic muscles and found them at intervals of about SO/a in 

 Geotrupes, SO^i in Miisca. Weiant (unpublished), found endings at inter- 

 vals of about 40[x in Pcriplaneta leg muscles though she was unable to obtain 

 a clear picture of the individual endings. In the leg muscles of Locusta the 

 endings are about 60/* apart. This kind of innervation may conveniently 

 be called multiterminal innervation (Ripley, 1954). 



The one, two, or three motor axons supplying a muscle unit travel to- 

 gether, bound by the same sheath right up to the point of contact, i.e., right 



cur/CLi 



APODBM 

 "slov^" f=/e/z£ 



MA//V A^jE-z^l/^ T/Zl/A/K. 



Fig. 3. Diagram to illustrate the pattern of innervation of a doubly innervated 

 insect muscle unit, based on the locust extensor tibae unit. 



