TECHNIC. 305 



'stains mucin orange-yellow. For the demonstration of mucin, more es- 

 pecially in alcoholic preparations, H. Hoyer (90) has recommended 

 thionin or its substitute, toluidin-blue. Indeed, the basic anilin dyes in 

 general seem to have a particular affinity for mucin. 



P. Mayer (96) recommends the following two solutions for 

 the staining of mucin: (i) Mucicarmin Carmin i gm., aluminium 

 chlorid 0.5 gm., and distilled water 2 c.c. are stirred together and 

 heated over a small flame till the mixture becomes quite dark. As soon 

 as the mixture has attained the consistency of thick syrup, 50% alcohol 

 is added and the whole transferred to a bottle in which it is shaken after 

 the addition of more alcohol. Finally, still more 50% alcohol is added 

 until the whole amounts to 100 c.c. Before using, this stock solution is 

 diluted tenfold with tap-water rich in lime-salts. (2) Muchematein : 

 () Aqueous solution 0.2 gm. of hematein is ground in a mortar con- 

 taining a few drops of glycerin; to this are added o.i gm. aluminium 

 chlorid, 40 c.c. glycerin, and 60 c.c. distilled water. () Alcoholic 

 solution 0.2 gm. hematein, o.i gm. aluminium chlorid, 100 c.c. 70% 

 alcohol, and i or 2 drops of nitric acid. Both of these solutions are used 

 for staining mucin in sections and thin membranes. By the use of these 

 methods the mucous acini of mixed glands are shown with ease and pre- 

 cision. Under favorable conditions the whole secretory and excretory 

 system of the gland may be brought out by Golgi's method (see this). 



In order to obtain a general structural view of the esophagus a 

 small animal may be selected, in which case small pieces of tissue are 

 fixed and imbedded in paraffin. If a large animal is used, the tissue is 

 imbedded in celloidin. 



The mucous membrane of the stomach should be fixed while 

 still fresh and warm, the best fixative for this purpose being corrosive sub- 

 limate. Mixtures of osmic acid are also serviceable, but fixing with cor- 

 rosive sublimate increases the staining power of the tissue. In order to 

 preserve the stomach and intestine in a dilated condition, they should be 

 filled with the fixing fluid and after ligation placed whole in the fixing agent. 

 In gastric mucous membrane that has been fixed either with corrosive 

 sublimate or alcohol, the parietal cells are easily differentiated from the 

 chief cells by staining. The most reliable and convenient method is as 

 follows : Sections fastened to the slide by the water-albumin fixative 

 method are stained with hematoxylin and then placed in a dilute 

 aqueous solution of Congo red until they assume a red color (minutes); 

 they are then washed with dilute alcohol until the parietal cells appear 

 red and the chief cells bluish (Stintzing). Almost all acid anilin dyes 

 have an affinity for the parietal cells ; hence the red stains may be com- 

 bined with hematoxylin and the blue ones with carmin. The chief cells 

 then take the color of the carmin or hematoxylin, and the parietal cells 

 that of the anilins. 



An accurate fixation of that portion of the small intestine possessing 

 villi is attended with great difficulty, since the axial tissue of the villi 

 shows a tendency to retract from the epithelial layer surrounding it 

 (the latter becoming fixed first); and as a consequence spaces are formed 

 at the summits of the villi which undoubtedly represent artefacts. A 

 good method is to cut pieces from tissue while still warm and fix in osmic 

 acid. If portions of the intestine be filled with alcohol or corrosive sub- 

 limate and thus dilated, both the glands and villi are shortened. The 



