124 MICROSCOPIC ANATOMY OF THE TEETH 



This penetration by blood-vessels may, perhaps, be looked 

 upon as a vestigial survival of the condition described by 

 the author in certain families of osseous fish in which the 

 enamel organ is permeated by blood-vessels or sinuses 

 enclosed in a delicate sheath, forming a" regular layer around 

 the forming enamel, to which further reference will be made 

 in describing the development of the enamel in fish. 



The Stellate Reticulum (%s. 73 and 74). There has been 

 some controversy and considerable difference of opinion as 



e. 



FIG. 72. Budding of the external epithelium (human tooth), s. Stellate, 

 reticulum ; e. external epithelium ; &. blood-vessels. (Photograph from a, 

 preparation of Mr. W. James.) (x 150.) 



to the structure and function of this layer. A great part of 

 this uncertainty has been caused, as was first pointed out 

 by Leon Williams, by the unsuitable methods of preparation, 

 and the bare skeleton of the stellate reticulum only has been 

 seen. 



The shrinkage caused by the use of alcohol in both fixing 

 and dehydration, and the further distortion caused by clear- 

 ing oils and Canada balsam, are fatal to such a delicate 

 tissue as the stellate reticulum, as they are indeed to many 

 others of a similar nature, and while these routine methods 

 are perfectly applicable to many preparations, they should 

 not be adopted in the investigation of tissues of this nature., 



