86 TISSUES OF THE NERVOUS SYSTEM. 



stripped off the external aspect of the vessel, spread out on an 

 object-glass, and covered in glycerin. 



Meissner's Plexus. The ganglionic nodules, occurring 

 in the course of the nerves which form Meissner's plexus, in 

 the submucosa of the intestine, may be studied as follows. 

 They are also well seen in longitudinal and cross sections of 

 intestine hardened in chromic acid, and still better in sections 

 parallel with the surface. Strips of intestine of the cat or dog 

 (after having been washed with half per cent, salt solution, or 

 water colored slightly with bichromate of potash) are steeped 

 for from forty minutes to an hour in half per cent, gold solu- 

 tion, and then exposed to light in distilled water, and finally 

 hardened in alcohol. Sections are then made in a direction 

 parallel to the serosa, of which of course those only are of 

 use which pass through the submucous tissue. Any one pos- 

 sessed of sufficient dexterity can obtain good preparations by 

 spreading bits of rabbit's intestine, excised and cleansed as 

 above described, on a piece of cork by aid of pins, with the 

 mucous surface uppermost. The mucosa is then worked off 

 as completely as possible with the fine-pointed forceps. Fine 

 flakes of loose tissue must be snipped with the aid of the 

 curved scissors, either from the deep surface of the mucosa, or 

 from the surface from which it has been severed. These are 

 either examined in salt solution in the fresh state, or treated 

 with gold for permanent preparations. 



Auerbach's Ganglia. The ganglia of Auerbach, which 

 are interposed between the transverse and longitudinal muscu- 

 lar layers, are demonstrated as follows : A portion of fresh intes- 

 tine of a rabbit or new-born foetus is blown out with the aid of 

 a glass tube. The operator must then try to strip off with the 

 forceps, from the external surface, a thin membrane, which will 

 be found to contain the serosa and the longitudinal muscular 

 layer. Strips of considerable extent may be thus obtained with 

 a little practice, and must be then treated with gold in the 

 usual manner. 



The ganglion cells, which occur in the genital organs, may 

 be best studied in sections or parts hardened in chromic acid, 

 or colored with gold and then hardened in alcohol. Good 

 preparations of sympathetic ganglia can be obtained from the 

 bladder of the rabbit. Bits of the fresh bladder are colored 

 with chloride of gold, and then steeped in acidulated water until 

 they swell out into a gelatinous translucent mass. Thin mem- 

 branous fragments stripped off with the forceps, or snipped off 

 with the scissors, are spread out and covered in glycerin. To 

 these preparations we shall recur, in connection with the dis- 

 tribution of the nerves among unstriped muscular fibres. 



Intimate Structure of the Ganglion Cells of the 

 Sympathetic System. In each ganglion cell (with the ex- 



