82 TRANSACTIONS OF THE [jAN. 11, 



ON SOME POINTS IN THE FORMATION AND DISTRI- 

 BUTION OF THE CERVICAL PLEXUS IN 

 CYNOMORPHOUS MONKEYS. 



By Geo. S. Huntington, 



The following paper contains the first of a series of observa- 

 tions on the structure of the Peripheral Nervous System of the 

 Simiadae, the purpose of the investigation including a study of 

 the formation of the spinal nerve-plexus, and of peripheral spinal 

 nerve-anastomoses, in an attempt to determine more accurately 

 their morphological significance and phylogenetic value. 



The material on which the following observations have been 

 made, comprises a number of individuals of the following species, 

 dissected during the past two years in the Laboratory for 

 Morphological Research of Columbia University : 



Cercopithecus diana, Macacus rhesus, 



" mona, " ochreatus, 



" pogonias, Cynocephalus hamadr^'as, 



Chlorocebus subagus, '' porcarius, 



Cercocebus fulginosus, " anubis, 



" collaris, " babouin, 



Macacus sinicus, " sphinx, 



" pileatus, Chseropithecus leucophcieus, 



" nemestrinus, Mormon maimon. 

 " cynoraolgus. 



The construction of the cervical plexus in these forms, by the 

 anterior divisions of the first four cervical nerves, resembles in 

 its main features the type usually followed in the human subject. 



A representative type is shown in Plate VII., Fig. I., w^iich 

 exhibits the plan of the right cervical plexus of a female Ilacacus 

 rhesus. 



The anterior branch of the First Cervical nerve gives off a 

 large communicating twig (Fig. I., 1), which passes forwards 

 and enters the sheath of the Hypoglossal nerve, dividing into a 

 bundle (Fig. I., 2), the fibres of which course centripetalh' in 

 the Hypoglassal sheath, and a peripherally^ directed bundle (Fig. 

 I., 3), which will be again referred to in discussing the forma- 

 tion of the deep cervical ansa and the innervation of the Infra- 

 hyoid muscles. 



The centrally directed bundle (2) gives off several small mus- 

 cular twigs to the Anterior Recti, but does not exhaust itself 



