CAKTILAGE. BONE. TEETH. 43 



rich in blood-vessels, which reach it through its pedi- 

 cle, contains, besides, a large number of nuclei and 

 young cells of an oval form, together with some 

 connective fibrillae ; its nerves, which appear some- 

 what later, accompany its vessels. It is covered by 

 an amorphous membrane* which, as Magitot has 

 shown, is incorrectly regarded as a portion of the 

 internal layer of the wall of the dental sac. This 

 border belongs really to the germ, and takes no part 

 in the subsequent formation of the ivory. Beneath 

 this there is a stratum of oval cells, arranged very 

 regularly side by side, with their long diameters per- 

 pendicular to the surface of the germ. The peripheral 

 extremity of each cell elongates into a thread-like 

 tube, which by degrees increases in size, and gives off 

 minute lateral branches ; in this manner a great 

 number of minute canals are formed, which run 

 parallel with each other to the* extreme limit of the 

 germ, communicating largely by their ramifications. 

 Thus the canalicuii of the ivory of the tooth are 

 developed from the superficial cells of its germ, each 

 cell, according to Kolliker,f by a process similar to 

 wire-drawing, elongating itself into a complete canal. 

 Whilst the dental canals are being thus developed, 



* Homogeneous basement membrane of Todd and Bowman. In his 

 account of the development of the teeth the author mainly follows 

 Goodsir. (Ed.} 



t A. Kolliker, Professor of Anatomy and Physiology in the University 

 of Wufzburg (Bavaria), author of the " Manual of Human Microscopic 

 Anatomy," which has been twice translated into English ; first by Pro- 

 fessors Busk and Huxley, and published by the Sydenham Society, 

 1853-54; and more recently, in a revised edition, by Dr. George 

 Buchanan, under the author's supervision. Parker, London. 1860. 



