THE NERVOUS SYSTEM. H9 



important question now arises, viz.: to ascertain what becomes of 

 these fibres, whether, after running a shorter or longer distance, 

 they terminate in the cord, or whether they all ascend to the 

 brain. It is well known, that until recently, most observers 

 have been of the latter opinion, which was founded less upon 

 direct observation than on the ground of probability, until 

 Volkmann, in his deservedly celebrated article, 'Physiology of 

 the Nerves/ shook it to its foundations, carrying the greater 

 number of physiologists with him. I also was among these, 

 until I had myself investigated the conditions, for there could 

 be no doubt that Yolkmann's theory connected, in the most 

 harmonious way, the anatomical facts and the results of 

 physiology as at that time exhibited. "NY hen I now, notwith- 

 standing this, abandon Yolkmann's theory of the termination 

 of the spinal nerves in the cord, I am induced to do so by 

 weighty reasons, and much regretting that I am unable to 

 maintain a view, which appeared to throw so much light upon 

 many difficult parts of the physiology of the nerves, and to be 

 in accordance with so many other anatomical conditions (ganglia, 

 invertebrate animals). 



[Yolkmann, in his hypothesis of the origination of the fibres 

 in the cord, relies upon the circumstance (1. c, p. 482, et seq.), 

 that the spinal cord is not of a pyramidal form with the base 

 above, as must have been the case had all the fibres of the 

 roots of the nerves ascended towards the cerebrum, but that it 

 rather presents a local increase of the nervous substance at the 

 points of origin of large nerves, which enlargement is not 

 confined to the grey substance, but equally involves the white. 

 That this is the case Volkmann shows from four transverse 

 sections of the spinal cord of the Horse, and from a comparison 

 of the diameter of the cervical cord of Crotalus horridus, with 

 that of all the nerve-roots of the same animal, which was 

 found to be eleven times greater than the former. He also 

 supports his view by the consideration: 1. that the enlarge- 

 ments of the cord are always regulated by the size of the 

 nerves of the extremities, being sometimes wanting and some- 

 times enormously developed; 2. that the cord, at the points of 

 exit of the largest nerves, instead of becoming suddenly 

 thinner, is in most cases enlarged ; and 3. that the origin of 



