480 MESSRS. F. GOTCH AND V. HOKSLEY 



fibrillated in their intimate structure,* shew a peculiar arrangement of one medullated 

 outgoing branch, and from the opposite side numerous subdividing branches. 



Spinal Ganglia. A word must here be interpolated on the structure of the 

 ganglion of the posterior root in its character as a simple nerve centre. 



All research t on the anatomical structure of these ganglia goes to show that their 

 corpuscles pass through a change in the course of their development, being at first 

 bipolar and afterward unipolar, and that any axis cylinder in relation to any such 

 corpuscle does not directly enter this but gives off a branch at right angles to the 

 ganglion cell, thus forming what has been termed a T-shaped junction. 



In addition, it has been shown} that there are fibres (as " determined " by the 

 degeneration method) which pass through the ganglion (spinal) into the posterior 

 root without coming into any relation with its cells. To sum up shortly, therefore, 

 it is evident that there are passing through a spinal ganglion numerous direct proto- 

 plasmic nerve channels. 



We have now to sketch further the afferent and efferent relations of the spinal 

 nerve centres with the encephalon, with the other centres in the spinal cord, and 

 with the periphery. 



Afferent Channels of Communication. The afferent paths may advantageously be 

 considered in reverse order to that just given. 



The afferent fibres in the posterior root are now known to have the following 

 destinations as regards the spinal nerve centres : 



1. Some pass the centres and, without communicating with them, enter the postero- 

 extemal column and finally course up the postero-median column to the nucleus 

 gracilis. 



2. Others enter CLARKE'S column where that is present. 



3. Others enter the posterior horn, and are lost in it. 



4. Others enter the posterior horn, but pass through it to enter the anterior horn. 



5. Some fibres bifurcate on their entry into the cord, one branch ascending and one 

 descending ; the branches end in a fine plexus in the grey matter (KOLLIKEH). 



The different fibres leaving the spinal nerve centre to connect with its neighbour 

 have never received absolute anatomical demonstration, but from the results of 

 physiological investigation their existence must be postulated. 



The afferent fibres connecting the spinal nerve centres with the encephalon have 

 been determined by the degeneration method to pass up the direct cerebellar and 

 antero-lateral tracts and have been traced as far as the cerebellum and pons, but no 

 further. 



* See particularly MAX SCHULTZE, and H. SCHULTZE, 'Arckiv f. Auat. u. Physiol.' FLEMMING. 

 HENLE'S ' Festschrift.' 



t See particularly RANVIER, ' Traite Technique d'Histologie.' His, ' Tageblatt der Naturforscher 

 Versammlung zn Berlin, 1886.' FRITSCH, ' Archiv f. Mikrosk. Anat.,' vol. 27, 1886. 



J MAX JOSEPH, 'Archiv f. Anat. u. Physiol.' (on BOIS-REYMOND), 1887, p. 307. 



