xxii Journal of Comparative Neurology. 



The studies here gathered together and translated comprise, as 

 Mendel points out in the brief Introduction, researches in the most 

 difficult fields. In view of Cajal's previous successes along similar 

 lines, it is with the highest expectations that we take up the work. 

 Nor are we disappointed. To give an adequate notice of each of the 

 sections, as outlined in the Table of Contents given above, would 

 mvolve practically the translation of the entire paper ; and indeed we 

 trust that such a translation may soon be provided by some one. We 

 can merely select at random a few of the author's suggestive results. 



In the first section he re-establishes his earlier discovery (con- 

 firmed by KoUiker, Held, Van Gehuchten) that the trigeminal gan- 

 glion cells are unipolar and that the process divides T-form into peri-' 

 pheral and central fibers, the latter inside the medulla exhibiting the 

 Y-shaped bifurcation so characteristic of sensory root-fibers in gen- 

 eral. He does not confirm Van Gehuchten's account that one limb 

 of the Y enters the so-called descending (or mesencephalic) root of 

 the trigeminus, but regards the latter as made up exclusively of mo- 

 tor fibers. These ascending (cephalic) fibers of the Y are short 

 and fine, resembling collaterals of the coarser descending fibers, though 

 they too give off collaterals which end in the substantia gelatinosa or 

 in the adjacent motor nucleus of the fifth nerve. Cajal thinks it im- 

 probable that any collaterals of the descending fibers (which consti- 

 tute the so-called " ascending root " of the trigeminus) effect such di- 

 rect reflex connections, but that they act only through the mediation 

 of the cells of the substantia gelatinosa. He confirms in the main 

 KoUiker's account, adding some details, of the way in which these 

 latter cells send their processes into a secondary central trigeminal 

 tract, which lies very near to the corresponding tract of the vagus. 



If we turn now to the seventh section of this contribution and 

 read the account of the sensory roots of the glosso-pharyngeus and 

 vagus, the resemblance to the sensory roots of the trigeminus, as de- 

 scribed in the first section, is striking. The trigeminal root is the 

 bearer of general cutaneous impressions from the head. Its fibers 

 find their terminal nucleus in the cells of the substantia gelatinosa 

 which are distributed along the mesal aspect of the so-called ascend- 

 ing, or spinal, trigeminal root for its entire length and down into the 

 the cervical cord, where they become continuous with the dorsal 

 cornu. In very much the same way the sensory roots of the ninth 

 and tenth nerves from the viscera and mucous surfaces, including taste 

 buds, enter the fasciculus solitarius, through the spinal portion of 

 which they too are brought into relation with the grey matter of the 



