1886.1 - 461 [Stowell. 



3. Nerves of common sensation with a specialized function and with 

 motor filaments. 



4. Nerves which directly or through their relation with N. sympathicus 

 indirectly control or modify glandular secretion. 



It is unsatisfactory to attempt to classify the function of N. tensor tym- 

 pani and the filament to the tentorium cerehelli. 



DESCRIPTION. 



Origin: The study of the entocranial portions of the trigeminus nerve 

 includes the description of the ental (deep) and the ectal (apparent) origins 

 of both portions. 



The ental origin has not been satisfactorily determined. Preliminary 

 work based upon Mondino's Golgi's perchloride of mercury method (Jour- 

 nal of Royal Microscopical Society, N. S. V., Part 5, p. 904, 16) indicates 

 a method for the solution of this difficult problem. 



The method for tracing nerve-tracts in the brain and spinal cord as pub- 

 lished in Brain, Vol. viii, p. 86, may prove serviceable in this connection. 



The impracticability of positively establishing the relations of the two 

 roots without serial transverse sections leaves the ental origin involved in 

 obscurity ; the following general relations, determined under a magnifying 

 power of 15-20 diameters, may serve to indicate the wide-spread origin of 

 this nerve, and also the necessity of making serial sections along a consid- 

 erable portion of the neuron. 



The fasciculi, by whose confluence the nerve-trunks are formed, may be 

 designated the 



Proximate roots: From morphological considerations alone it would 

 be natural to treat this nerve as having two roots, the motor and the sen- 

 sory. 



Radix motoria : The motor root generally — not invariably — consists of 

 two packets, the dorsal or cerebellar, and the ventral or epicoelian. 



The fasciculi of the dorsal root often lie free of the pons, or they inter- 

 digitate with the pons ; they may be traced along with medipeduncular 

 fibres to the cerebellum ; the motor root frequently contains fibres from 

 the pons. 



The larger or ventral root generally lies wholly free of the pons (some 

 of its fibres may interdigitate with the pons). It forms the caudal border 

 of the emarginate pons, and may be traced caudad of the prepeduncle to 

 the floor of the epicoele, about 2 mm. laterad of the meson, at which point 

 the fibres bend abruptly ventrad. 



The two-fold origin of this root is suggestive of difference of function. 



Radix 8ensoria: The sensory root seems to have a four-fold origin ; these 

 roots, by virtue of their course, may be nanied cephalic, dorsal, caudal 

 and ventral roots respectively. Rx. cephalica may be traced with some 

 radical fibres of the prepeduncle into the floor of the epicoele, and thence 

 cephalad to the region of the preopticus. 



Do not these fibres suggest an entaj origin similar to the anthropotomic 



