XI V] NERVE FIBRES 113 



4. Similar nerve fibres in later stage (20 days 

 after section). The myelin has nearly all disappeared, 

 a few fibres still show here and there rows of fat 

 globules. 



NOTES. 



Medullated nerve fibres. 



Teasing osmic acid specimens. Nerves, either normal or de- 

 generated, are placed in 1 p.c. osmic acid for 1 to 24 hours, 

 washed in running water, put in 30 p.c alcohol for a day and 

 teased in dilute glycerine. Nerves may be kept for a day or two 

 in dilute glycerine before teasing, but the contrast between the 

 small medullated and the non-medullated fibres becomes less 

 distinct. In strong glycerine the small medullated fibres will 

 be more or less decolourized ; in alcohol the non-medullated fibres 

 become dark brown and the whole brittle. If the nerve cannot 

 be teased at once it is perhaps best kept in a saturated aqueous 

 solution of potassic acetate. 



In degenerated nerve treated with osmic acid leucocytes 

 crowded in the early stages of degeneration with fatty glo- 

 bules, and in the late stages with yellowish -brown granules 

 (probably from the neurokeratin), are seen. These vary much 

 in number in nerves in different parts of the body and even in 

 different regions of the same nerve. In most stages of de- 

 generation, but especially the later ones, elongated masses of 

 yellowish-brown granules are seen, which appear to be free and 

 not contained in leucocytes. After the medulla has been ab- 

 sorbed the general appearance in teased specimens is like that of 

 a non-medullated nerve. The nuclei in a degenerated nerve may 

 be stained with picrocarmine or with a special nuclear stain. 

 An increase of nuclei takes place about the 6th to the 16th day ; 

 two nuclei are commonly seen close together, but dividing nuclei 

 are rarely seen. 



The grey rami of the rabbit contain very few medullated 

 fibres, those of the cat and dog may have few or many; the 

 L. 8 



