230 ON THE DEVELOPMENT OF THE TEETH 



outwards. They are firmly connected together, and have a radiated 

 position in respect of the papilla. It is to the layer formed by these 

 cells that Raschkow has assigned the name of enamel membrane. 

 Taking this view of the construction of the enamel organ, I cannot 

 perceive any grounds for the division of it into two parts suggested by 

 the description of Raschkow. It is obviously nothing more than a 

 single organ, and the difference in the form and arrangement of the cells 

 must simply be regarded as a transition of the first and second kinds 

 into those of the third — the latter being in the state of preparation 

 for the reception of the calcareous salts. 



" The mucous membrane which rises in the form of a ring fence 

 around the papilla developed from the dental groove is the future 

 dental capsule. At an early period it is difficult to determine to what 

 extent the internal surface of the growing follicle differs from mucous 

 membrane. That it does so may be inferred from the change in 

 function which it assumes ; and at a later period, when the follicle is 

 about to close, the difference in its organic character becomes striking- 

 ly obvious. For example, it is white, silvery, loose, and rugous, and 

 easily falls into folds, and, under the microscope, offers the appearance 

 of a number of minute cells possessing characters ■widely different 

 from those of the epithelium. 



" A portion of the internal lamina of the dental capsule, placed 

 under the microscope, shows it to be composed of layers of cells 

 loosely arranged, and separated by interspaces equal to half the 

 diameter of the cell. The cells are oval in shape, and provided with 

 one or more distinct nuclei, and they contain in their interior a small 

 quantity of granular matter. The internal lamina of the dental 

 capsule maintains but a slight degree of adhesion with the enamel 

 organ, and possesses no vessels. Subjacent to it is a network of 

 blood-vessels, supported by a web of areolo-fibrous tissue formed by 

 the interlacement of fine homogeneous filaments, among which 

 nucleated cells are not unfrequently observed." — p. 107. 



Saccular Stages. — When the sac closes — 



" The space between the pulp and the sac becomes filled with 

 a fluid secretion which distends its cavity, and often produces a 

 conspicuous enlargement in the situation of the tooth." — p. 108. 



" On the part of the capsule corresponding with the sides and neck 

 of the crown is a flat portion of the enamel organ, which is destined 

 to the formation of the enamel in that situation. This lamina has a 

 well defined inferior border at a later period in the growth of the 

 enamel organ ; the appearance which it presented of a gelatinous mass 

 is lost, and the substance contracts into a membranous layer. At this 



