HISTOLOGY OF THE TEETH. 151 



I per cent, solution of methyl-green in alcohol and water (lo parts 

 alcohol, 90 parts of water) for several minutes ; this will over- 

 stain. Next, place in absolute alcohol, which will remove the 

 excess of green. When the right shade is procured, place on the 

 slide, add oil of cloves to clear, and then mount. To double- 

 stain with eosin and green, first stain with eosin, and then wash 

 with water, to which has been added a few drops of hydrochloric 

 acid; this fixes the stain. Then over-stain in green, decolourise in 

 alcohol, place on a slide, add oil of cloves to clear, then mount. 

 Having thus obtained, stained and mounted, a series of specimens, 

 let us study them, and see what they will show, commencing with 

 our smallest foetal pig 2^ centimeters in length, of which we have 

 made horizontal transparent sections of its inferior maxilla. The 

 first sections remove the surface of the gum, and simply show 

 epithelial tissue ; but a few sections deeper, we find a furrow or 

 band filled with small round cells. 



The outer sides of this band are composed of cylindrical cells. 

 This band extends the entire length of the jaw ; on either side of 

 the band the jaw is made up of embryonal tissue, while on its 

 labial and lingual aspect we find epithelium. 



If osmic-acid solution be injected underneath the mucous- 

 membrane of the mouth of a perfectly fresh 8 or 10 cm. foetal 

 pig, and it then be immersed in a solution of equal parts of the 

 same solution and alcohol to harden, the morphological changes 

 in the cells of the enamel organ will be arrested. If we lift the 

 mucous-membrane from its bed after the tissue is sufiiciently 

 hardened, the enamel organs will adhere and bring up w^ith them 

 their papillae. You thus isolate the enamel organ from the sur- 

 rounding calcified tissue, imbed and make sections, and these 

 sections will show that what appears to be the recticulum of the 

 stellate cells is in reality a broad mesh, the reticular appearance, 

 with large interspace between, resulting from the shrinkage of 

 the cells in the process of hardening with Miiller's fluid, chromic 

 acid, etc. — these latter failing to arrest the morphological changes. 

 In the meshes of the stellate, also prepared by the osmic acid 

 method, which has stained the cells a very dark brown, are seen 

 numerous minute granular bodies, which have a high refractive 

 power. If a few drops of dilute nitric acid be put on the slide 



