KliSTEVEN ON THE A2TAT0MT OF THE SPINAL CORD. 381 



longitudinal fibres are subjected to anatomical demonstration by- 

 transparent sections. The axis-cylinder of the nerve-tube becomes 

 tinged with the colouring matter, while its surrounding sheath remains 

 untinged. In this way the transverse fibres become distinguishable as 

 they traverse the bundles of longitudinal fibres, the dyed ends of which 

 thickly dot the field of the object glass of the microscope, (fig. 1.) 



By gentle pressure of a fresh nerve the solid cylinder may be 

 protruded, and thus demonstrated in its recent state. This is readily 

 efiected in the nerves of fishes {e.g. Cod). The author of an elaborate 

 essay on " General Nerve Physiology," in a late No. of the British 

 and Foreign Medico- Chirui-gical Eeview,* observes: — "As to the 

 tubular nature of the axis- cylinder, we once thought that we had 

 convinced ourselves of this in the anterior nerve-roots of the ox. But 

 on examining our preparations, in which the axis cylinder gave the 

 appearance of having a double contour, with a finer microscope, the 

 tubular appearance cannot be made out, and the axis cylinder, under 

 a very high power, appeared to consist of a finely granular homogene- 

 ous substance. We have now little doubt that the axis cylinder is 

 a solid or semi-solid fibre, continuous with the contents of the 

 nerve-cell." The same writer expresses his concurrence in Mr. 

 Lockhart Clarke's opinion that Stilling was, in his examinations of 

 nerve structure, misled by his mode of making his preparations. 



A transverse section exhibits also the relations of tlie fissures of 

 the cord — the anterior and posterior median, and several lateral or 

 radiating fissures which admit the passage of vessels. The general 

 distribution of the latter is beautifully shown by the use of trans- 

 parent injections.t The principal source of supply is by one or, 

 sometimes, two arterial trunks passing down the anterior fissure, 

 piercing the anterior commissure to send a branch on each side of the 

 central canal, then rapidly dividing and subdividing into almost as 

 many and as minute branches as there are nerve processes. So nu- 

 merous are their ramifications and anastomoses, that a network of 

 minute meshes is formed in the grey matter, and its superior vascu- 

 larity strongly marked, (fig. 2.) A second source of vascular supply is 

 from the pia mater of the aurface. Vessels may be seen traversing the 

 white columns, and passing inwards to the grey matter, giving ofl" 

 branches to their connective tissue and fibres in their course inwards. 

 In the Boa the size of the vessels of the grey matter is, relatively to 

 that of the higher animals, large, and their course distinct. 



The connective tissue consists of a fine net- work between the fibres 

 and blood-vessels of the columns. In the calf this tissue may readily 

 be seen to be interspersed with a multitude of minute cells or nuclei, 

 which send out processes or fibres in different directions to assist in 

 forming the net-work of areolar tissue. The smallest cells of the 



* July 1862, p. 3. 

 t The writer has traced the vessels in many exquisite specimens of injected cord, 

 prepared by C. M. Topping, 7, Haverstock Street, City Road. 



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