QUARTERLY CHRONICLE OF MICROSCOPICAL 



SCIENCE. 



Histology. — Teeth. — Development of the Milk and Per- 

 manent Teeth in Man. By J. Kollman, with two plates, 

 eighty-five pages, KoU. u. Sieb. Zeitschrift, 2iid part, 1870. 

 The author of this lengthy paper gives certain conclusions at 

 which he arrives. Every embryonic tooth, he says, possesses 

 a tooth sac. From the string or cord of connection between 

 the original epithelial organ of the primary tooth-germ and 

 the enamel-organ of the secondary tooth germ, arise certain 

 club-like branches with round cells ; these are quite free 

 from any connection with vascular loops, but each bud, or 

 epithelial-branch, as the author calls it, can give origin to a 

 tooth. Upon this arrangement de])ends the abnormal increase 

 of the number of the teeth. The second teeth always take 

 their first origin in the median line, never at the side of the 

 milk tooth. Cell-metamorphosis in the enamel-germ of the 

 second tooth proceeds with extreme slowness. The cell- 

 brood of the oral mucous membrane persists in the remnant 

 of the epithelial organ which is spoken of above as the string 

 of connection (verbindungstrang), and the processes and 

 buds from this cord for years retain the power of starting the 

 development of teeth. Dentes accessorii and dcites proliferi 

 are entirely different in their origin. The membrana pi'ce- 

 formativa is really as such an artificial product. It is, in fact, 

 the young condition of the enamel cuticle, of which some 

 persons have erroneously denied the existence. The cells of 

 the enamel-germ become variously modified in the course of 

 development into {a) stellate cells of the enamel pulp ; (b) 

 later they form the innermost layer of the tooth sacculus, 

 after the transformation of the enamel cells, and they take on 

 the character of young connective tissue cells which finally 

 become changed in all those animals with a cement layer on 

 the crown of the tooth into (c) bone-cells or osteoblasts. 

 The membrana adamantinae and membrana eboris are best 

 comprehended as lamellar epithelium. The one is produced 

 from the cells of the embryonal Malpighian rete mucosum, 

 the other from connective tissue cells. The enamel arises 



