420 



SPECIAL HISTOLOGY. 



Fig. 145. 



the spinal accessory nerve in this case loses all that is remark- 

 able in it. Now, if the spinal cord in man be examined with 

 reference to the above points, it will present, in almost all of 

 them, exactly the contrary of what Yolkmann noticed in 

 animals. Iri the first place, the white substance constantly 

 increases in thickness from below upwards, and the enlargements 

 of the cord depend upon an increase of the grey substance more 

 than anything else. That this is the case, is evident at a 

 glance, when sections, such as are represented, 

 after nature, in fig. 145, are compared with each 

 other, and it also admits of being estimated 

 in numbers (vid. ' Mikroskop. Anatomie/ II, 1, 

 p. 431). 



This fact being established, it remains to deter- 

 mine the proportion borne by the white substance 

 in the superior cervical region to the peripheral 

 nerves. For this purpose I instituted Volk- 

 mann's measurements in man, and in a male 

 and female body estimated all the roots of the 

 spinal nerves on the left side ; I determined, from 

 the ascertained diameters, the transverse sectional 

 surfaces of all the nerves in square lines, and 

 compared with them the transverse sectional 

 area taken with the utmost possible nicety, of 

 the white substance of the spinal cord, at the 

 level of the second cervical vertebra. 



It is quite true that there was now evident a very con- 

 siderable difference against the spinal cord; but when the very 

 great attenuation of the nerve-fibres of the roots, at their 

 entrance and in their further course in the cord, was brought 

 into account, which was not done by Yolkmann, the matter 

 was entirely altered, and it became clear that the cord in the 

 male subject contained more than sufficient fibres to furnish 



Fig. 145. Five transverse sections through a human spinal cord, hardened by 

 chromic acid, to show the relative proportions of the grey and white substances, — of 

 the natural size: A, from the conus medullaris, the diameter of the cord being 3§'"; 

 B, from the lumbar enlargement, transverse diameter 4f", antero-posterior 41"'; C, 

 from the dorsal part of the cord, 4^'" and 3jj"'; D, from the cervical enlargement, 

 G§'" and 4.1'" ; E, from the superior cervical portion, level with the second nerve, 

 6f and 4f". 



