112 



MANUAL OF HISTOLOGY. 



tion. The nuclei will then be stained a brick-red, while the 

 sheath of Schwann, and, in fact, the whole nerve, will be stained 

 yellow. It is said that, if the axis-cylinder projects, it will be 

 stained a bright red, though twenty-four hours may be required 

 to effect the staining. In my hands picro-carmine has not 

 proved so successful a coloring agent as some others. 



Staining witJi the nitrate of silver. The sciatic or any 

 peripheral nerve may be employed. Expose it without re- 

 moval in a frog that has just been killed. Then dry up all 

 fluid from about it, and pour on a solution of the nitrate (1 to 

 1,000). In this way the nerve-fibres will be made rigid. They 

 are then to be removed with a pair of delicate scissors, and 

 placed in a flat vessel containing a little more of the solution. 

 After a few minutes the nerve will look turbid, and then it 

 should be cut out and washed in distilled water, and exposed 

 to the sunlight. In a variable time (ten to fifteen minutes) the 

 turbid appearance will give way to a brown coloration. Exam- 

 ining a single funicu- 

 lus or bundle in gly- 

 cerine, it will be seen 

 that it has an endothe- 

 lial coating of one or 

 more layers (Fig. 44). 



If another f uniculus 

 be separated with fine 

 needles, 1 the same care 

 being taken to spread 

 the fibres apart and not 

 tease, and so lacerate 

 them, it will be seen 

 that each fibre con- 

 tains a series of Latin 



crosses at certain pretty regular intervals. The transverse bar 

 of the cross corresponds to the " annular constriction" seen 

 in Ranvier's node, while the axis-cylinder forms the longitudi- 

 nal bar. Close observation with high powers will show that 

 this latter is marked by transverse lines of a dark brown or 



then evaporated to dryness, the residue dissolved in 100 c.c. of water, and filtered. 

 If the solution is not clear, he adds more ammonia, evaporates, and then dissolves as 

 before. 



1 Milliners 7 are the best. 



FIG. 44. Fnniculns or Nerve Bundle covered with Endothe- 

 lium (Epithelium). From the sciatic of the frog. Hartnack, 

 object. 4, oc. 2. 



