150 A MANUAL OF DENTAL ANATOMY. 



concentric laminae like an onion has already been mentioned, 

 and Mr. Rainie was aware that albumen actually entered 

 into the composition of the globule, since it retained its 

 form even after the application of acid. 



But Professor Harting has shown that the albumen left 

 behind after the treatment of a calcospherite with acid is 

 no longer ordinary albumen ; it is profoundly modified, and 

 has become exceedingly resistant to the action of acids, 

 alkalies, and boiling water, and in fact resembles chitine, 

 the substance of which the hard skins of insects consist, 

 rather than any other body. 



For this modified albumen he proposes the name of 

 " calcoglobulin," as it appears that the lime is held in some 

 sort of chemical combination, for the last traces of lime are 

 retained very obstinately when calcoglobulin is submitted 

 to the action of acids. 



The " calcospherite," then, has a true matrix of calco- 

 globulin, which is capable of retaining its form and structure 

 after the removal of the great bulk of the lime. 



Now it is a very suggestive fact that in the investigation 

 of calcification we constantly meet with structures remark- 

 able for their indestructibility : for example, if we destroy 

 the dentine by the action of very strong acids, or by 

 variously contrived processes of decalcification, putrefaction, 

 &c., there remains behind a tangled mass of tubes, the 

 " dentinal sheaths " of Neumann, which are really the 

 immediate walls of the dentinal tubes. 



Or if bone be disintegrated by certain methods there 

 remain behind large tubes, found to be the linings of the 

 haversian canals (Kolliker), and small rounded bodies, 

 recognisable as isolated lacunse ; and in the cuticula dentis 

 we have another excellent example of this peculiarly inde- 

 structible tissue. 



In point of fact, as will be better seen after the develop- 

 ment of the dental tissue has been more fully described, on 



