90 PRACTICAL HISTOLOGY. 



are present except the enamel, and probably also much of 

 the pulp will be wanting. 



(H.) The dentinal tubules will be readily seen. 

 Carefully examine the pulp close to the dentine for odonto- 

 blasts. These are nucleated cells that send one or more 

 somewhat stiff processes from their outer aspects into the 

 dentinal tubules, constituting the dentinal fibres, or fibres 

 of Tomes. The odontoblasts are, however, very liable to 

 be lost during the softening of the tooth. Serves and blood- 

 vessels and a delicate connective tissue are also found in 

 the pulp, but these need not be looked for in this prepara- 

 tion. 



133. The structure of the pulp of the full-grown tooth can only be 

 investigated by breaking the tooth across with a hammer. The broken 

 tooth should then be hardened for twenty-four hours in per cent osmic 

 acid. 



134. The odontoblasts and fibres of Tomes maybe seen in sections 

 of the teeth in situ, when they are very young and still within the den- 

 tal sacs. 



135. The dentinal tubules may be isolated by boiling a softened 

 tooth for about ten minutes in I per cent sulphuric acid. The tubules 

 appear to be calcified membranes, imbedded in a calcified tissue some- 

 what similar to that of bone. The latter disappears when boiled in the 

 dilute acid. 



MUSCLE. 



136. Non-Striped Muscle. Methods of Preparation. 

 a. Kolliker's method for the isolation of the fibres con- 

 sists in placing a piece of fresh intestine or stomach in 

 dilute nitric acid (acid one part, water four parts) for 

 twenty-four or thirty-six hours. The muscular fibres are 

 hardened and assume a yellow colour, while the fibrous 

 tissue that binds them together is softened and dissolved. 

 The acid is then removed by washing in water. The nu- 

 cleus in each fibre may be clearly brought into view by 

 logwood staining. The fibres are separated by teasing. 



b. The fibres may also be separated by teasing after 

 maceration for two days or so in dilute alcohol ( 284). 



c. The fibres may also be prepared by the gold method. 

 For this purpose portions of the muscular coat, from the 

 small intestine of a rabbit or other animal recently killed, 



