JOURNAL OF MICROSCOPICAL SCIENCE. 



EXPLANATION OF PLATES IV & V. 



Illustrating Mr. Tomes's paper on the Development of 



Teeth. 



The lettering is the same in all the figures. 



a. Oral epithelium. 

 h. Bone of the jaw. 



c. Neck of the enamel organ, connecting it with the oral epithelium. 



d. Formative pulp of the dentine = dentine papilla. 



e. Enamel organ. 



f. Stellate tissue of the enamel organ. 



g. Cap of formed enamel. 



t. Completed teeth, already in use. 



Fig. 1. — From the lower jaw of a kitten, just bom. 



To the left of the larger tooth germ, which belongs to the milk tooth, is 

 tfie smaller and younger germ of its permanent successor. The enamel 

 germ of the permanent tooth-sac still retains its connection with the neck 

 of the enamel organ of the deciduous tooth, whence it was originally derived. 



Fig. 2. — From a green lizard. 



A young tooth germ, consisting of an enamel organ with an excessively 

 long neck, and a dentine germ. 



Fig. 3. — From a green lizard (same specimen as No, 2), showing the 

 relative positions of the older tooth and of the successional tooth germs. 



Fig. 4. — Lower jaw of common English snake. 



The successional tooth germs, four in number, are seen in transverse 

 section, owing to the fact that the developing teeth lie recumbent and 

 almost parallel to the long axis of the jaw. 



Fig. 5. — Upper jaw of common frog. 



To the inner side of the base of the tooth is that dipping inwards of 

 epithelium (c) which is the first step towards the formation of a new enamel 

 organ and new tooth germ. 



