370 



THE TISSUES. 



veral of these occurring in a thin section of dentine seen under the 

 microscope, causes the wall to appear shaded within, and thicker 

 than it actually is. (Fig. 231, a, &,' c.) The branches of the tubuli 

 are, 1st. Principal divisions, leaving the main trunk at acute angles; 

 and, being repeated two to five times in the thickness of the den- 

 tine, amount to four, eight, or even sixteen in all. These terminate 

 in a granular layer between the dentine and enamel, or between the 

 fibres of the latter, or unite in pairs to form loops in the dentine. 

 2d. The anastomosing branches are very minute and numerous, and 

 most so in the root of the tooth. These and the primary divisions 

 just described, are seen in Fig. 232. Their finest subdivisions are 

 not more than Q^^Q of an inch in diameter. Seen in dried sections, 

 the tubuli appear black; being filled with air merely, as is the case 

 with the pores and lacunae of dried bone. Certain projections are 

 found in the dentine, called dentinal globules ; l which are bounded 

 by irregular spaces called interglobular spaces. The former are found 

 mostly in the outer portion of the dentine, though they also occur 

 in the deeper parts. They are globular or capitate, as represented 

 by Fig. 233. 



Fig. 233. 



r 



Section of dentine, -with dentinal globules, and interglobular spaces filled with air. Magnified 350 



diameters. (K<:lliker.) 



The interglobular spaces are naturally filled by a soft substance, 

 like tooth-cartilage (osteine), and possessing a canaliculated structure, 

 like the dentine itself. 



II. THE ENAMEL. 



The enamel forms a layer completely investing the dentine of 

 the body of the tooth. It is thickest on the crown and the outside 



1 Hoppe finds the globules to be distinct cells with nuclei. 



