44 PRACTICAL HISTOLOGY. 



ARRANGEMENT OF NERVE-FIBRES TO FORM A NERVE. 



PREPARATION. Place pieces of the human or other sciatic nerve, cut into pieces one inch 

 long, into chromic acid and spirit (p. xxxi), or Miiller's fluid and spirit (p. xxxii), for ten days, and 

 after hardening in alcohol make transverse sections in the ordinary way. Stain a section in 

 logwood, and, if it be desired, another in carmine, and mount them in dammar. They both 

 show the same details. 



EXAMINATION (L). The various bundles composed of nerve-fibres are held together by a 

 common framework of connective tissue the epineurium arranged so as to form a sheath 

 around and between the various bundles, and in it may be found transverse sections of the 

 large blood-vessels which supply the nerve with blood. Round each bundle observe a special 

 sheath the perineunum composed of lamellated connective tissue with flattened connective- 

 tissue cells between them. The spaces between the lamellae represent lymph-spaces. (Indicate 

 these bundles in PI. VIII., Fig. 10.) 



Study a nerve-bundle. Observe it is made up of many nerves cut transversely ; only the 

 stained axis-cylinders are indicated. 



(H). Study the epi- and perineurium ; observe the cut ends of the nerve-fibres varying in 

 diameter, and the section of the axis-cylinder stained red or violet and surrounded by a trans- 

 parent circular area, which represents the myeline or white sheath of Schwann ; outside this 

 a faint circle, indicating the primitive sheath. Between the nerve-fibres may be seen very 

 delicate connective tissue the endoneurium with here and there a small blood-vessel in it. 

 (Indicate the stained axial cylinders and the cut ends of the nerve-fibres in PI. VIII., Fig. 1 1.) 

 If the hardening process has been continued for a month or longer, concentric rings may be 

 observed in the white substance of Schwann. {Indicate these in PI. VIII., Fig. 12.) Longi- 

 tudinal sections of a nerve prepared as above may also be studied. 



THE CONNECTIVE-TISSUE ELEMENTS OF A NERVE. 



PREPARATION. Take a small fragment of a nerve which has been hardened in one-sixth 

 per cent, solution of chromic acid for ten days, and after staining in logwood, tease it 

 thoroughly in a drop of glycerine. 



EXAMINATION (H). Observe the nerve-fibres. The axis-cylinder, stained violet, will 

 easily be recognised amidst the coagulated myeline. It is specially interesting to trace the 

 axis-cylinder across a node of Ranvier. Observe the connective tissue, some of it in the form 

 of delicate lamellae, with here and there oval nuclei stained violet lying on them, and also de- 

 tached flattened plates the connective-tissue corpuscles each containing a large oval violet 

 nucleus. 



FRESH NERVE-FIBRES OF THE SPINAL CORD. 



PREPARATION. With scissors snip off a small fragment of the white matter of a fresh 

 spinal cord of an ox or sheep, place it on a dry slide, do not add any fluid, put on a cover- 

 glass, and compress it into a thin layer. 



EXAMINATION (H). Observe the drops of myeline, easily recognised by their concentric 

 markings and the absence of a nucleus, and very delicate nerve-fibres with bulgings or am- 

 pullae upon them, due to the pressure of the cover-glass on the nerve-fibres, which here are 



