DESCRIPTION OF PLATE ]iXYll—eonHmed. 



nections of these nerves with one anotlier and with the third nerve, 

 the principal brandies of the third nerve, and the course and distri- 

 bution of the fourth and ninth nerves, at sta^e n. No single section 

 could show all or even the greater number of the parts represented in 

 either of these figures, as they lie at very different levels. X 25. 



Fig. 11, drawn to show the whole course and relations of the fifth 

 nerve and its connections with the third and seventh nerves. The 

 figure also shows the fourth nerve, and the terminal distribution of 

 the hyoideau branch of the seventh. 



Fig. 12 shows the whole course of the seventh nerve and its 

 branches, with the exception of the hyoideau branch (shown iu the 

 preceding figure) ; also the course and distribution of the ninth nerve, 

 and certain branches of the fifth and tenth nerves. 



Fig. 13. — Longitudinal and vertical section through the head of an embryo 

 of stage N ; the figure, which is taken from two consecutive sections, 

 shows tiie origin and main trunk of the tliird nerve, the root of the 

 fourth, and the roots, course, and distribution to the rectus externus 

 of the sixth nerve. X 20. 



Figs. 14 and 15. — Diagrammatic longitudinal and vertical sections through 

 the head of an embryo of an age intermediate between stages o and 

 p. X 15. 



Fig. 14 shows the roots of origin of the third, fifth, and seventh 

 nerves together with the course and distribution of certain of their 

 branches and the mutual connections between these three nerves. 



Fig. 15 shows the dorsal root of the seventh nerve, the ophthalmic 

 branches of the fifth and seventh nerves, the ramtis ophthalmicus pro- 

 fundus, the fourth nerve, the maxillo-mandibular branch of the fifth, 

 and the buccal and palatine branches of the seventh. 



Fig. 16, — Transverse section through the head of an embryo of stage Q, 

 shortly before the period of hatching. Shows the origin, course, and 

 distribution of the fourth nerve, and its close proximity to the 

 ophthalmic branches of the fifth and seventh nerves. 



