500 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



the idea that the origin of the auditory nerve from the cerebel- 

 lum, already expressed in general terms by Foville and Schro- 

 der v. der Kolk, might be rejected. I must however insist, 

 before entering into details, that the exclusive partly decus- 

 sating, partly non-decussating connection of the auditory nerve 

 with the cerebellum indicates that it belongs to a different 

 category from the other nerve roots ; in favour of which view, 

 which I have long maintained, and have supported on micro- 

 scopic grounds, I may adduce the experience of Clarke and 

 Dean. 



In accordance with the general plan of this essay, I ought 

 in the next place to refer to the tracts that connect the cere- 

 bral lobes through the peduncle with the centres of origin of 

 the auditory nerve, a connection which, upon physiological 

 grounds, in Man we should expect to find as large and exten- 

 sive as that of the retina through the optic nerve. It is very 

 remarkable, however, that no such connection of the centres of 

 origin of the auditory nerve with the cerebral peduncle is 

 discoverable. 



We obtain, indeed, in the regions of emergence common to 

 the auditory and facial nerves, the most striking appearance of 

 a complete bending round of the posterior longitudinal fasci- 

 culus into the centres of origin of the auditory nerve at its 

 side (fig. 256, 8, vin), which in the first instance led me to re- 

 gard the posterior longitudinal fasciculus as an auditory cord 

 or column. Extremely successful preparations, however, subse- 

 quently made from the pons of the Dog by the staining method, 

 showing the most delicate details of structure, have convinced 

 me that the posterior longitudinal fasciculus is only traversed 

 by the central auditory fasciculus, so that it appears precisely 

 as if it curved round, whilst it really descends to the anterior 

 columns of the spinal cord (Stilling). 



Stilling indeed already noticed that the straight fibres of 

 the raphe pass into the external roots of the auditory nerve 

 (strise medullares) ; by far the greater number, however, have 

 no connection with the cms cerebri, as they can be followed on 

 the other side of the middle line as fibrse arcuatse in the crus 

 cerebelli. 



After all that has been said, we may regard it as certain that 



