82 MICROSCOPIC ANATOMY OF THE TEETH 



combined with the poor formation of the cement substance 

 and of the outer portion of the prisms, due to the enamel 

 organ at the time not having acquired a perfect function '. 



That dentinal tubes pass into human enamel in places 

 there can be no doubt ; they are seen to do so in a great 

 number of preparations, both stained and unstained. This 

 is, however, doubted by Pickerill, who considers the appear- 

 ance of tubes crossing the boundary line is due to the over- 

 lapping of the dentine and enamel. 



In properly stained preparations, however, these tubes 

 are seen to pass in so deeply that no such confusion 

 could possibly arise, good thin sections showing the enamel 

 and dentine quite clearly separated. Moreover, the fuchsin 

 method also shows, as referred to above, that the 

 laminae between the horizontal layers of prisms also stain. 

 Pickerill was quite unable to convince himself when 

 using the Von Beust method of staining with alcoholic 

 fuchsin, taken up from the pulp cavity by capillary attrac- 

 tion, that stained tubes passed into the enamel from the 

 dentine. It is a little difficult to understand why he failed 

 to see them, as by this method the spindles and the tubes 

 are often deeply stained and in many places air-bubbles 

 have preceded the staining fluid to the ends of the spindles. 

 He also is of opinion that ' it by no means follows that 

 because a highly volatile and deeply penetrating stain like 

 alcoholic carbol fuchsin 1 may pass occasionally across the 

 amelo-dentinal junction that serum or lymph would do the 

 same '. It surely is inconceivable that a staining solution, 

 which after all is not so highly volatile, should pass into 

 a dead tissue more perfectly than the fluids of the living 

 body in a living tissue. 



It seems much more probable that the permeation by 

 serum or lymph from the circulating blood would be more 

 thorough than that obtained by any artificial stain. 



If this contention were true it would nullify the value of 

 any stains, alcoholic or other, in demonstrating the existence 

 of channels or spaces in a tissue. What is usually required 

 in histological investigation, especially on the teeth, is 



1 Carbol fuchsin is not employed, but a simple solution of fuchsin in 

 alcohol. 



