NATURE OF THE CUTICULA DENTIS. 323 



fissures will often be found extending down from the grinding 

 surfaces through half or more of the thickness of the enamel. 

 These fissures, which are generally contracted at their orifices, 

 are seldom found empty, but are usually tenanted by a dark 

 brown mass, the structure of which is rendered indistin^ 

 guishable by its opacity. 



In some instances these dark masses are more transparent, 

 and are seen to be made uj) of round or oval bodies closely 

 packed together, in the centres of which are very commonly 

 dark radiated forms exactly like bone-lacunse. They are 

 almost always of brownisli colom-, and the branched air- 

 containing spaces in their centres vary in size and form from 

 mere fissures to full-sized lacunal cavities. 



In fig. 2 a single one of these bodies is represented 

 occupying and filling up a minute dejjression on the enamel 

 of a molar tooth, whilst in fig. 3 a cluster of them is seen 

 lying against one side of a much larger fissure in another 

 tooth. In fig. 4, Avhich is a transverse section through a 

 cylindrical pit in the enamel, a similar large cluster of these 

 peculiar bodies is seen. Out of thirty-six deeply fissured 

 teeth I was able to distinctly see these forms in twelve, while 

 indications of their existence were seen in several others, so 

 that they are by no means uncommon. 



No one can look at these bodies without being struck 

 witli their close resemblance to the lacunse of bone, or rather 

 to those of cementum; and when they are compared with 

 those encapsuled lacunoe which are so common in the thick 

 cement of herbivora, and which also occur abundantly in 

 human cement when thickened by disease, the resemblance 

 is seen to be complete. For the sake of comparison, a figure 

 (fig. 5) has been given of these encapsuled lacunae occurring 

 in the thickened cementum of a human tooth, and these are 

 to be regarded, as Drs. Bcale and Waldeyer have pointed 

 out, as remains of the formative osteoblasts, the contours of 

 which, under ordinary circumstances, become lost during the 

 progress of calcification. 



The very frequent occurrence of these " encapsuled 

 lacunae," or " osteoblasts," wherever a deep fissure affords 

 sufficient sj)ace for their development, having been noted, it 

 remains to show their connection Avith Nasmyth's membrane. 

 An unworn molar or premolar tooth, the grinding surface of 

 Avhich shows indications of a deep fissure, having been 

 selected, longitudinal sections through the crown and fang 

 are to be rubbed down on a hone until sufficiently thin for 

 examinations ivith a half-inch objective. The section is to 

 be laid on the slide and treated Avith dilute hydrochloriG 



