138 STUDENTS HISTOLOGY 



will be entirely dissolved. The enamel prisms may be demonstrated by 

 treating broken fragments with dilute acid for a short time only. 



Sections should be stained with carmine and picric acid and mounted in 

 glycerin. For the study of the development of teeth, foetal jaws may be 

 treated as just described; and, when properly decalcified and hardened, should 

 be infiltrated with celloidin, sectioned, and stained. 



TRANSVERSE SECTION OP FANG OF HUMAN DECIDUOUS CANINE 

 TOOTH DECALCIFIED (Fig. 92) 



OBSERVE : 

 (L.) 



1. Division into pulp, dentine, cementum, and perice- 

 mentum. 



2. Line of junction of pulp and dentine. (If the elements of 

 the pulp are intact, note the layer of deeply stained odontoblasts 

 next the dentine.) 



3. External limit of dentine. (Note here the deeply stained 

 granular line of Purkinje. This is the location of the interglobu- 

 lar spaces. The deep color is due to the staining of the contents 

 of their cells.) 



4. The striae of the dentine. (The dentinal canals and stained 

 contents.) 



5. The laminated cementum. (The yellowish pink dots on 

 the lacunas.) 



(H.) 



6. Elements of the pulp, (a) The layer of odontoblasts. 

 (Note their internal processes connecting with other cells of the 

 pulp; and the external processes passing into the dentinal 

 canals.) (6) The sparsely fibrillated character of the pulp- 

 tissue, (c) Sections of vascular loops. (The nerve-elements 

 may be demonstrated, particularly if the section be made near the 

 apex of the root, where the fibers are medullated. The terminal 

 fibrillae are non- medullated.) 



7. Dentinal elements. () The dentinal canals. (&) The 

 dentinal sheath. (Better demonstrated in transverse sections.) 

 (c) Dentinal fibers. (In transverse sections the canals are well 

 shown lined with a membrane of extraordinary tenuity, with the 

 fiber appearing as a central dot.) (d) Fine dentinal fibers near 

 the outer limit, (e) Interglobular spaces. (An occasional cell 

 may be made out in the larger spaces. They were formerly sup- 



