122 MANUAL OP HISTOLOGY. 



in the digestive tract. Preparations of the cceliac ganglion of 

 the frog may be made according to the methods that have al- 

 ready been described. The aorta and bulbus arteriosus of the 

 frog are recommended by Klein, and the gold method is the best 

 to show them. It was in these corpuscles of the green tree-frog 

 that Beale noticed a spiral fibre. It was a delicate one, wind- 

 ing round the axis-cylinder, finally going off in an opposite 

 direction. He also thought, from an examination of the gan- 

 glia in the mammalia, that the same fibre existed in them. Sub- 

 sequently Julius Arnold corroborated his views, and even de- 

 scribed a network of fibres which was connected with the 

 nucleolus, and extended through the corpuscle, at its final 

 exit forming the spinal fibre. Recent observers, however, have 

 failed to confirm Arnold's opinion, and even the existence of a 

 spiral fibre is held to be in doubt. 1 These corpuscles, which are 

 either globular or oblong, may appear to be apolar, unipolar, 

 bipolar (when two processes are given off in the opposite direc- 

 tions), or multipolar (when two are given off in the same direc- 

 tion, or several are given off in various directions). 



Meissner 1 s plexus. This network, named after its dis- 

 coverer, is situated in the submucous tissue, and consists of 

 nerve-bundles of medium size, which have nodular enlarge- 

 ments studded with nuclei at certain points. An excellent 

 way of securing them is the following : Take a piece of cat's 

 intestine, three or four inches in length ; cleanse thoroughly 

 by passing through it a stream of water ; then ligate one ex- 

 tremity. Fill an ordinary two-ounce syringe with a solution of 

 the chloride of gold (i). Slip the nozzle into the other end of 

 the intestine, and, tying it in, inject with such force as to dis- 

 tend the gut to its utmost extent without bursting. Then pass 

 another ligature round the gut beyond the nozzle, and draw it 

 tight. Remove the syringe, and place the specimen in an open 

 vessel containing the same solution, but allowing fully one- 

 half of it to be uncovered by the liquid. After twenty-four 

 hours the part thus exposed will have taken a mauve or violet 

 color. Then remove from the liquid, and open with scissors, 

 let it partly dry, and, seizing the mucous membrane with the 

 forceps, tear it off in pieces. The submucous tissue will then 



1 Key and Retains did not find the spiral fibre in the human species, but in the 

 frog occasionally. Op. cit. Many other excellent observers agree with them. 



