ON THE DEVELOPMENT OF THE TEETH 229 



papilla rises above the level of the surrounding fence of mucous 

 membrane, a small quantity of whitish matter may be detected in the 

 groove between the papilla and the follicle — this is the enamel organ. 

 Not unfrequently the whitish matter has the appearance of granules 

 which seem to have been separated from the surface of the follicle. 

 These granular masses have a pearl white aspect, and are soft and 

 friable. Under the microscope they are seen to be composed of cells 

 which separate from one another upon the slightest compression. 

 The cells offer considerable variety in respect of size and shape, some 

 being small and round, others large and flattened, and furnished at 

 one extremity with a delicate prolongation ; while others again are 

 elongated and narrow, and have a defined and regular margin. They 

 contain nuclei and nucleoli, and are covered on their interior by 

 minute granules, which are also found in considerable abundance in 

 their interstices." — p. 104. 



" In the numerous examinations which I have made of the stages 

 of growth of the teeth here described, the enamel organs did not 

 appear to me to be attached either to the papilla or to the surface of 

 the follicle. This may probably arise from the circumstance that all 

 the embryos which I dissected had been kept for some time in diluted 

 spirits of wine." — p. 105. 



He then quotes Raschkovv's account of the structure in the Lamb 

 and Calf, and goes on to say, — 



" In my own investigations made with the aid of one of the best 

 microscopes of modern construction, and with a magnifying power of 

 one-tenth of an inch focal distance, I found the enamel substance to 

 be composed of cells of three different kinds. 



" The first kind of cells are found in the interior of the organ, and 

 compose its loose, soft, and easily compressible texture. They are 

 flattened and triangular in form, and connected to adjacent cells by 

 means of delicate filaments prolonged from one of their angles. 

 The.se appendages have no analogy with the filaments of areolo- 

 fibrous tissue, as declared by Raschkow. I have seen them in 

 connexion with the cells of other tissues, and the error on the part of 

 this observer must have arisen from the use of low microscopic powers. 



" The second kind of cells are oval in shape, and form an envelope 

 to the preceding : they are situated both upon the superficial and 

 •deep aspect of the latter. 



" The third kind of cells occupy the deep stratum of the enamel 

 organ, lying in contact with the dental papilla. They are narrow and 

 ■oblong in shape, and are arranged closely side by side ; one of their 

 extremities being in relation with the papilla, the other being directed 



