98 PRACTICAL HISTOLOGY. 



nerve fibrils may be seen in the processes, especially at the 

 junction of these with the cell, into the granular protoplasm 

 of which they may be traced. If the cells and their pro- 

 cesses have been very successfully isolated, it may be seen, 

 as Deiters pointed out, that each cell has one process the 

 " axial cylinder process " which undergoes no division, 

 and at some distance from the cell becomes enclosed in 

 the medullary sheath, and thus becomes a white fibre. All 

 the other processes remain gray; they repeatedly divide, and 

 form a reticulum in the gray matter of the cord. 



The nerve cells of the brain will be examined with that 

 organ. 



157. Examine a preparation of the pear-shaped cells 

 of the ganglia of the frog's heart with a power of about 800 

 diam. Such a preparation may be made as follows (Beale) : 

 Carminise the auricular septum of the frog's heart. Ma- 

 cerate for some days in glycerine (i oz.), and glacial acetic 

 acid (5 drops) ; isolate the ganglia by teasing with needles 

 under a dissecting microscope. Preserve in glycerine. 



As pointed out by Beale each cell has two processes : 

 a straight fibre resembling in position the stalk of a pear, 

 and a spiral fibre coiled round it for some distance. 



PERIPHERAL NERVE TERMINATIONS. 



The methods for demonstrating these in the various 

 sense organs will be conveniently studied with these organs 

 themselves. 



158. Plexus of Fibrils. This has been already seen 

 in the cornea stained with gold, 154. 



A fine plexus of nerve fibrils may also be beautifully shown in the 

 tail of the tadpole of the green tree frog (Hyla arborea), prepared as 

 recommended by Klein. Place the tail of a tadpole in which the pos- 

 terior extremities are just appearing in \ per cent solution of chloride 

 of gold for from thirty to forty minutes ; wash in distilled water, and 

 leave it in the water exposed to diffuse daylight for twenty-four hours 

 or so. Then strip off the epidermis from one side with a pair of 

 forceps, and mount in glycerine with the inner surface of the epidermis 

 uppermost. The removal of the epidermis is facilitated by immersion 

 in absolute alcohol for fifteen minutes or So. If this preparation be 

 successful, a plexus of nerve fibrils will be found close to the epidermis. 



