DEVELOPMENT OP THE ENAMEL 181 



function of separating out the lime salts, a function which is 

 apparently discharged by the ameloblasts in mammalian 

 tooth germs ... so that one is driven to the conclusion that, 

 the stroma once formed, it is able to draw into itself the 

 required lime salts and to deposit them at that point which 

 is furthest from the vessels '. 



A paper by Mr. Thornton Carter on the development of 

 the enamel in the Hake has recently appeared. He states 

 that the cells of the external epithelium and the ameloblasts 

 ' remain in contact throughout the whole life history of the 

 enamel organ ', and describes the changes which take place 

 in the ameloblast cells. He denies the disappearance of 

 these cells and states that they do not disappear but become 

 elongated and vacuolated, and there is no evidence that the 

 ameloblasts become transformed into a stroma which 

 becomes incorporated in the enamel. For a consideration 

 of the evidences in favour of this view the reader is referred 

 to the original paper (56). 



The present author has found large nucleated cells lying 

 in a stroma in the Haddock (Gadus ceglefinus), the whole 

 bearing a strong resemblance to a stellate reticulum, but not 

 being able to procure absolutely fresh material was unable 

 to carry out the investigation. The cell structure of the 

 enamel organ cannot be properly studied in imperfectly 

 fixed material, as the author found in his first attempts 

 to demonstrate the structure of the enamel organ of Sargus 

 ovis. Mr. Carter states that an interval of even five minutes 

 after death, before fixation, is sufficient to interfere with 

 the finer reactions of cells to stains, and specimens of fish 

 should be placed in the fixing solution as soon as caught. 



Tomes confined his investigations chiefly to the enamel 

 organs of the Gadidse. He also examined the development 

 of the enamel in Sargus and Labrus, but was unable to 

 obtain satisfactory preparations owing to difficulties which 

 he considered ' almost insuperable ', the tooth germs being 

 so deeply placed in the bone that fixing agents did not 

 reach them. 



It appeared to the author that if the jaw of a fresh 

 specimen of Sargus ovis was cut up at once and placed 

 in the fixing solution, this difficulty might be overcome, and 



