SEGMENTS OF TRIGEMINAL NERVE-GROUP 265 



and of facts derived from post-mortem dissections, that one may 

 venture to designate the portion of the nucleus from which the 

 innervation of each individual ocular muscle comes. He gives Starr's 

 table, the latest of these numerous attempts, begun by Pick. Accord- 

 ing to Starr, the nuclei of the nerves to the individual muscles are 

 arranged from before backward, thus — 



m. sphincter iridis. m. ciliaris. 



m. levator palpebral, m. rectus intemus. 



m. rectus superior. m. rectus inferior. 



m. ohliquus inferior. 

 Further, the evidence of the well-known physiological experi- 

 ments of Hensen and Volckers that the terminal branches of the 

 oculomotor nerve arise from a series of segments of the nucleus, 

 arranged more or less one behind the other in a longitudinal row, 

 leads them to the conclusion that the nuclei of origin are arranged as 

 follows, proceeding from head to tail : — 



It is instructive to compare this arrangement of Hensen and 

 Volckers with the arrangement of the origin of these muscles from 

 the premandibular cavity as given by Miss Piatt. 



Thus she states that the most posterior part of the premandibular 

 cavity is cut off so as to form a separate cavity, resembling, except 

 in position, the anterior cavity ; this separate, most posterior part 

 gives origin to the inferior oblique muscle. She then goes on to 

 describe how the dorsal wall of the remainder of the premandibular 

 cavity becomes thickened, to form posteriorly the rudiment of the 

 inferior rectus and anteriorly the rudiments of the superior and 

 internal recti, a slight depression in the wall of the cavity separating 

 these rudiments. The internal rectus is the more median of the 

 two anterior muscles. In other words, her evidence points not only 

 to a fusion of somites to form the premandibular cavity, but also 

 to the arrangement of these somites as follows, from head to tail : 

 (1) internal rectus, (2) superior rectus, (3) inferior rectus, (4) inferior 



