INTRODUCTION. xHu 



of the pulp. Fine branches of nerves accompany the capillaries 

 and terminate also in loops. 



The primary cells of the papilliform pulp, the " grana aequalia 

 globosa" of Purkinje, are described by him as pre-existing to the 

 appearance of vessels and nerves in the pulp ; they are undoubtedly 

 unaccompanied by the blood-vessels at their first aggregation to 

 form the papilla ; but they bear the same relation to the capillary 

 net-work at the base of the papilla, which the subsequently formed 

 cells do to the capillaries that extend into the substance of the 

 papilla or pulp, when it is more developed. The primary cells 

 and the capillary vessels and nerves are imbedded in, and sup- 

 ported by a homogeneous, minutely sub-granular, mucilaginous 

 substance, the * blastema.' The cells (PI. 1, fig. I , a) which are 

 smallest at the base of the pulp, and have large, simple, subgranular 

 nuclei (ib. a'), soon fall into linear series directed towards the peri- 

 phery of the pulp : where the cells are in close proximity with that 

 periphery, they become more closely aggregated, increase in size, 

 and present the following changes in their interior. A pellucid 

 point appears in the centre of the nucleus which increases in size 

 and becomes more opake around that central point, rendering the 

 compressorium requisite for its demonstration. A division of the 

 nucleus in the course of its long axis is next observed (ib. b). In 

 the larger and more elongated cells, still nearer the periphery of the 

 pulp, a subdivision of the nuclei has taken place, and the subdivisions 

 become elongated with their long axes vertical or nearly so to the 

 plane of the pulp, and to the field of calcification (ib. c). The 

 subdivided and elongated nuclei become attached by their extre- 

 mities to the corresponding nuclei of the cells in advance ; and the 

 attached extremities become confluent (ib. d). Whilst these changes 



d 2 



