72 EXPLANATION OF THE PLATES. 



Fig. IL Section from the same medulla, a little higher up, showing the antero-lateral portions. 

 On each side of the raphe are seen the roots of the sixth or abducens, and a little further outwards is 

 seen the facial root passing inwards towards its nucleus. Between the two roots is seen one of the 

 upper olivary bodies. 



Fig. 12. Section showing the postero-lateral portion of the same specimen of which the antero- 

 lateral portion is giveii in Fig. 11. In the upper right hand corner is seen a portion of the flocculus. 

 The formation and development of both roots of the auditory, as well as of the fibres radiating through 

 the restiform body and serving to connect them, arc well shown in this figure. The v.ery numerous 

 bundles passing from the posterior portion of the auditory nucleus back into the cerebellum are very 

 conspicuous in the upper part of the figure. 



PLATE IV. 



Fig. 13. Transverse section from the sheep, showing the postero-lateral portion of the medulla. 

 The restiform body is now pushed backwards towards the cerebellum, and the posterior auditory root 

 is seen to be intimately connected with the flocculus. The connection between both portions of the 

 auditory nucleus and the cerebellum is very conspicuous. In the lower part of the figure part of the 

 facial course is seen, the root being now very large and distinct. 



Fig. 14. Antero-lateral portion of the sapie specimen as the preceding figure, showing the course 

 of the facial roots towards their decussation at the raphe as well as the development of the upper 

 olivary bodies. 



Fig. 15. Section from the same medulla, a little lower down than the preceding, showing the central 

 portions on each side the raphfe. The form of the fourth ventricle at this height is well seen, with the 

 projecting lingula or linguetta laminosa derived from the cerebellum. The course and destination of 

 the nerves of the sixth pair are well seen, and anteriorly the broad band of wavy fibres constituting 

 the trapezium. 



Fig. 16. Transverse section from the medulla of the sheep, still higher up, showing the gradual 

 disappearance of the facial roots, just before the root of the fifth is developed. The broad band of 

 fibres constituting the pons Varolii is seen in front. 



PLATE V. 



Fig. 1*1. Section of the human medulla just at the decussation of the pyramids. 



Fig. 18. Transverse section from the same, a little higher up, showing the formation of the raphfe 

 and the hypoglossal and spinal accessory nuclei. 



Fig. 19. Section from the same medulla, still higher, in which the nuclei are very conspicuous, the 

 central gray mass being elongated posteriorly in a very remarkable manner. The restiform and post- 

 pyramidal nuclei are very consj)icuous, and anteriorly the olivary bodies have made their appearance. 



Fig. 20. Transverse section from the same medulla, still higher up, showing the formation of the 

 fourth ventricle, and the complete development of the hypoglossal and vagal nuclei. 



PLATE VI. 



Fig. 21. Transverse section from the human medulla, showing the further development of the 

 nuclei and olivary bodies. 



Fig. 22. Transverse section from the same medulla, showing the complete opening of the fourth 

 ventricle, along the floor of which lie the hypoglossal, vagal and auditory nuclei, the latter just making 

 its appearance on the outer side of the vagus nucleus. 



Fig. 23. Section from the same, still higher up, showing the blending into a single mass of the 

 nuclei seen in Fig. 22, the vagus nucleus being pushed outwards towards the apex of the mass. 



