5.24 Dr. G-. Thin on the Anatomy of 



a series of bulgings, so that its lateral (optical) borders are designated by 

 irregularly waving lines. One set of delicate cells can be seen closely 

 following the sinuosities of the substance, while another set, more external, 

 lie in a straight direction parallel to the longitudinal axis of the fibre. 

 "Where the medulla is constricted, there is a clear space between these 

 two sets of cells, which are in contact at the convexities formed by the 

 bulgings. 



By adhering to the broad principle that wherever there is a nucleus 

 there is a cell, the existence of a great number of cells surrounding the 

 medulla of a nerve-fibre can be demonstrated in another way. If a nerve 

 is placed in absolute alcohol for twenty-four hours and then very gently 

 disentangled from the sheath in glycerine^ a cover-glass put on and solution 

 of hsematoxylin drawn through the field by filter-paper, the nuclei of the 

 fibres stain first, and their number soon becomes very striking. If the 

 field is allowed to become saturated and obscure with the dye, and then 

 subsequently cleared up by acetic acid, those fibres which have not 

 suffered by the manipulation are literally dotted over with nuclei. The 

 number is so great as at once to dispel the idea that they can be accounted 

 for by the sheath of Schwann. The nuclei of the sheath can often be 

 distinguished from the others by their more external position relative to 

 the nerve and a deeper tint. Figure 19, Plate X., is drawn from a pre- 

 paration made in this way. 



The ring which, as E-anvier was the first to show, snares the medullated 

 fibre is well seen when the nerve is treated by absolute alcohol or the 

 saturated potash solution, both of which leave the medulla untouched. 

 As at the seat of this constriction the medulla is deficient, and as the 

 nerve-fibre is bathed in lymph, it is evident that there must be at these 

 points a very intimate connexion between the lymph-fluid and the axis- 

 cylinder of the nerve. This has been already indicated by Banvier in his 

 essay on the lymphatic nature of the nerve-sheaths, and receives greater 

 force now that we know that flat cells, indicative of lymphatic structures, 

 are situated on. the fibres themselves. 



The use of hsematoxylin is as advantageous in demonstrating the large 

 nuclei of the flat cells of the nerve-sheaths as it is in showing those of 

 tendon. 



Banvier has observed that in transverse sections of nerves the sheaths 

 and connective tissue surrounding the fibres stain more deeply with car- 

 mine than the surrounding tissue does. 1 have made a similar observation 

 in the nerves of the skin in gold preparations which had been macerated 

 in acetic acid. In this case the concentrically arranged connective tissue 

 of the nerves is conspicuous by its pearly whiteness. But as we know 

 that the surrounding corium is equally rich with the nerve in lymphatic 

 structures, the cause of the difference in colour must be sought elsewhere, 

 and will probably be found in relative differences in regard to the ar- 

 rangement of the elastic tissue. 



