118 



MANUAL OF HISTOLOGY. 



same distances apart as in the other form of fibre already men- 

 tioned. 



Preparation in osmic acid and pier o-car mine. Remove 

 the pneumogastric in the following way, from a cat that has 

 just been killed : Having exposed the nerve, slip under it in 

 situ a long narrow strip of cork, to which, pin down the nerve 

 with some adjacent tissue, all of which may be removed at 



once and placed in a solution 

 of osmic acid (11,000) for 

 twenty -four hours ; the nerve 

 may then be separated from 

 its attachments and placed 

 in the picro-carmine solution 

 for still another twenty -four 

 hours. The excess of the col- 

 oring agent may be removed 

 by dipping for a few seconds 

 in acetic-acid solution (J- per 

 cent.), and then the nerve 

 may be placed in alcohol, 

 afterwards in water, and fin- 

 ally mounted in glycerine. 

 It will be seen that the nerve- 

 fibres are stained a reddish 

 yellow, while the nuclei are 

 brick-red. The picric-acid 

 yellow is apt, however, to 

 diffuse. Careful separation 

 of the fibres may show that 

 they branch, as shown in Fig. 

 48, A, B ; and yet this char- 

 acteristic, which Eanvier in- 

 sists upon, is by no means 

 easy to see in most of the fibres, in fact it requires much care- 

 ful work before it is apparent. The myelinic nerves will be dis- 

 tinguished by their greater average size, their dusky, granular 

 medulla, broken at points, and by the axis-cylinder, which, 

 if it does not project, may be seen winding spirally along be- 

 neath its medullary coat. In them, too, as a rule, each in- 

 terannular segment contains but one nucleus. 



Preparation of Remak" 1 s fibres in hcematoxylin. One of 



FIG. 48. Fibres of Remak. A, Pneumogastric 

 of the cat haeiuatoxylin specimen : a, nerve nu- 

 clei ; &, appearances of branching ; c, connective- 

 tissue sheath. B, Same. Picro-carmine specimen. 

 The branching in this case is more evident. C, 

 Same haematoxylin specimen. The necklace ap- 

 pearance is >shown at a. 



