THE TEETH. 617 



the general arrangement, the size of the lacunas, and the number and ramifi- 

 cations of their offshoots. 



The walls of the lacunae and the coarser offshoots, if viewed with a highly 

 magnifying lens, appear interrupted at their peripheries by light spaces, which 

 lead into a light, delicate net-work, piercing the whole basis-substance to 

 such an extent that only the meshes have to be considered as the fields of cal- 

 cified glue-yielding basis-substance. Each lacuna contains a plastid with a 

 central nucleus the cement-corpuscle. The nucleus sometimes is relatively 

 large and surrounded only by a narrow seam of bioplasson ; while in some 

 small lacunas a body of the appearance of a nucleus is present without a 

 noticeable amount of surrounding bioplasson. The net-like structure of the 

 plastids is plainly visible on all cement-corpuscles. From their periphery con- 

 ical offshoots arise, the coarser of which penetrate into the larger offshoots of 

 the lacunae, while the finest offshoots traverse the light rim between the wall 

 of the lacuna and the periphery of the plastid, being directed toward a light 

 interruption on the boundary of the lacuna. 



Cement-corpuscles, on the average, are round or spindle-shaped bodies, 

 the long diameter of which corresponds to the direction of the lamellae. In 

 teeth of juvenile and middle-aged persons we meet with cement-corpuscles 

 surpassing three or four times the size of ordinary ones, in which two or three 

 nuclei are visible. Instead of multinuclear bodies, a number of medullary 

 nucleated elements may fill a large lacuna. Numerous cement-corpuscles 

 send broad and branching offshoots through the basis-substance in a vertical 

 or oblique direction to the lamellae, and not infrequently a direct union is 

 established between two or three cement-corpuscles by means of such large 

 offshoots (see Fig. 262). 



In some teeth, broad, spindle-shaped spaces pierce the cementum in a 

 radiated direction, all of which contain bioplasson with delicate offshoots 

 directed toward the net-work in the basis-substance. Nay, sometimes medul- 

 lary spaces traverse the lamellas in different directions, which, besides a vary- 

 ing number of medullary elements, contain capillary blood-vessels, evidently 

 in connection with the capillaries of the pericementum. These formations 

 may be considered as remnants of the embryonic condition of the cementum, 

 and are never present in large numbers. All plastids within the cementum, 

 though greatly varying in shape, agree in being connected with each other by 

 the delicate net-work which pierces the basis-substance. 



At the periphery of the cementum, on the line of the connection with the 

 pericementum, the net-work of the bioplasson is usually very broad, and the 

 fields of the basis-substance show a prevailing globular appearance. Also, 

 numerous spindle-shaped plastids are seen in connection with the cementum 

 in an oblique arrangement, forming the transition into the structure of the 

 pericementum. Between the calcified eementum and the striated connective 

 tissue of the pericementum there often exists a narrow zone, occupied by 

 closely packed spindle-shaped bodies only. 



The connection between dentine and cementum is established either by a 

 gradual change of one tissue into the other, without a distinct line of demar- 

 cation, or there exists a boundary formed by a more or less marked wavy line, 

 presenting irregular, bay-like excavations. Lastly, it occurs that between the 

 bay-like excavations and the dentine there is interposed a stratum of the 

 structure of cementum, with a gradual change of the tissue of the former into 

 that of the latter. 



