*jo"u?nL.Ma;Ti87a'] Regeneration of the Sfiual Cord. 237 



These are the sizes of these elements : — 



Millimetre. 



Spheroid and stellate cellules : diameter of the cellule .. .. 0'0128 



„ „ „ nucleus .. .. 0-0096 



„ „ „ nucleolus .. 0-0016 



Bipolar cellules : great diameter 0-0208 



„ small diameter 0-0080 



These cellules are perfectly identical with the cellules taken 

 from different portions of the grey substance of the spinal cord in 

 healthy frogs. These are therefore nervous cellules. They differ in 

 nothing from the cells of the human cord, save in some secondary 

 characters; they are smaller than the latter, but this reduction 

 affects only the protoplasm ; the mean dimensions of the nucleus 

 are nearly equal to those of the human cord cells. 



2. Besides the preceding cellules we find corpuscles of different 

 dimensions (but nearly always greater than those of the cellules) ; 

 they are generally of a round form, and are composed of an accu- 

 mulation of angular granulations of a deep yellow, or sometimes 

 even quite black colour. These are very probably nervous cells 

 attacked by pigmentary metamorphoses (Fig. 2). 



3. Certain elements intermediate between the two preceding. 

 Some of these are like nerve-cells, devoid of prolongation, but 

 already containing, grouped around the nucleus, granulations like 

 those which compose the large pigment corpuscles. The others, 

 larger and apolar, are almost completely invaded by the pigmentary 

 matter; the nucleus appears as a circular uncoloured spot, and the 

 nucleolus has disappeared. 



4. Thick and slightly-flattened fibres, in which may be seen 

 elongated nuclei. In all respects they resemble the fibres of Bemak. 



5. Slender varicose fibres, far less numerous than the preceding. 

 They are identical with the amyline fibres of the nervous centres. 



If one completely removes the gelatinous substance which unites 

 the ends of the cord, it is found that the two surfaces of the section 

 have changed form. That of the cephalic extremity of the cord is 

 in some measure etalee, and recalls the appearance of the surface of 

 the section of a healthy cord still surrounded by its ])ia-mater. 

 The caudal end affords an opposite form, and resembles a sort of 

 stump (^moiynon). 



Microscopic examination shows in both ends of the cord altera- 

 tions which extend to two millimetres beyond the surface of the 

 section. The large fibres appear still normal; but the slender 

 fibres are more varicose, and are nearly entirely decomposed (near 

 the surface of the section) into globules of myelene. The cellular 

 elements present the same appearances as the cells which are met 

 in the uniting gelatinous substance. 



