NERVOUS PLEXUSES OF INTESTINE. 221 



glass vessel of water containing just enough acetic 

 acid to be sour to the taste, and the vessel is covered 

 and allowed to stand in a warm place freely exposed 

 to the sunlight (see p. 96). After two days its color 

 will be found to have changed to a dark violet. A 

 few drops of methylated spirit may then be added 

 to the fluid ; this serves to aid the reduction of the 

 gold and to prevent the growth of fungi. In another 

 day or two the tissue will be so dark as to appeal- 

 almost black. A portion is then removed to a glass 

 dish of water and prepared in the following way : 

 In the first place, the glandular mucous membrane 

 is separated from the rest of the intestinal wall 

 either by tearing it off with forceps or by scraping 

 it away with the end of a blunt scalpel. There now 

 remain the serous and two muscular layers, together 

 with the submucosa. To the inner surface of the 

 latter the muscularis mucosae may be still adherent. 

 The separated fragments of the mucous membrane 

 are got rid of by pouring away the water first used 

 and substituting fresh, and then an attempt must 

 be made by aid of two pairs of forceps, to peel the 

 submucosa off from the inner surface of the muscular 

 coat. Of course if the muscularis mucos?e has been 

 left, tluit will form a part of the layer which is thus 

 removed. The separation must be done slowly and 

 carefully, so as to get as large a piece as possible 

 intact. When this is accomplished satisfactorily a 

 slide is immersed in the w r ater, and the portion of 

 submucosa so detached is floated on to it, and 

 re'moved from the water. Its further preparation 

 consists in allowing the excess of water to run off, 

 applying a cover-glass, making sure first of all that 

 the layer is free from folds, and then allowing gly- 

 cerine to pass under the cover-glass and replace the 

 water as this evaporates. 



Returning to the remainder of the piece of intes- 

 tine, the next process consists in picking away bit 

 by bit with forceps the comparatively thick layer of 

 circular muscular fibres. This is not a difficult ro- 



