The Mid-Winter Meetings. 1 85 



some afferent neurones must have two " local signs " according to the point at which 

 they are stimulated. In considering the distribution to the various segments, 

 correction must be made for the splitting fibers. 



When this is done, it is found that the unit area of skin received the same num- 

 ber of afferent fibers in either the thigh, shank or foot. In a similar way, a study 

 of the muscular afferent fibers shows that the muscles are uniformly innervated 

 by muscular afferent fibers according to the unit weight of muscle. 



The Electric Organ of Astroscopus as Compared with that of Other Fishes. By 

 Charles F. Silvester, Princeton University. 



Concerning a New Ganglionic Mass of the Hind-brain, the Corpus Ponto-bulbare. 



By Charles R. Essick, Student of Medicine, Johns Hopkins University. 



A ganglionic mass accompanied by a layer of myelinated fibers is found over- 

 lapping the restiform body just caudal to the dorsal cochlear nucleus. It forms 

 a direct lateral process or extension of the ganglion mass of the pons. It is con- 

 stantly present in all human brains, though in some brains it reaches a greater 

 size than in others. Its relations and general characteristics are constant. It 

 makes its appearance on the ventro-lateral surface of the pons near the emerging 

 root bundles of the trigeminal nerve and extends backward, passing between the 

 roots of the facial and acoustic nerves. It continues caudalward passing dorsal 

 to the glossopharyngeal nerve and ends on the dorsal surface of the restiform body, 

 forming part of the lateral boundary of the fourth ventricle. It may end as a prom- 

 inent tongue-shaped mass or may spread out as a thin coating of the restiform body 

 that is only discernible microscopically. 



The Migration of Medullary Cells into the Ventral Nerve-roots of Pig Embryos. 



By F. W. Carpenter and R. C. Main, University of Illinois. 



In sections of pig embryos 11 mm. long, medullary cells were observed appar- 

 ently migrating from the neural tube in company with the fibers of the ventral 

 nerve roots. These cells have been found just inside the external limiting mem- 

 brane in an intermediate position half in and half out of the neural tube and in 

 the base of the nerve root just outside the limiting membrane. A few sections 

 show continuous lines of medullary cells, touching end to end and reaching from 

 the nidulus across the boundary of the tube into the proximal part of the nerve 

 root. These migrant cells do not appear to be directly connected with the embry- 

 onic nerve fibers. A few were observed undergoing mitotic division. Evidence 

 of a similar migration of medullary cells has been seen in sections of a cat embryo. 

 In these medullary elements escaping from the neural tube, we recognize the 

 "indifferent cells" of Schaper. Such cells remaining in the medullary wall become 

 either supporting elements (neuroglia cells) or nervous elements (neurones). Those 

 which escape, in part at least, probably contribute to the formation of the sheaths 

 of Schwann, which are supporting in function. Whether any migrant indifferent 

 cells become the nerve cells of sympathetic ganglia we are at present unable to 

 say. 



Glycogen in the Nerve Cells of the Brain and Spinal Cord of Larval Lampreys and 

 in the Central Nervous System of the Amphioxus from Naples. By Simon H. 

 Gage, Cornell University. 



