TEETH. 565 



calcareous matter becomes crowded and consolidated; as 

 the process advances, the bone thickens, and a series of 

 grooves, of a stellate form as in the annexed cut (fig. 307, 

 No. 2), are found upon its surface, 

 which become gradually con- 

 verted into canals for the pas- 

 sage of blood-vessels. 



In certain forms of disease, 

 many of the soft parts of the 

 human body are converted into 

 cartilaginous and bony masses, 

 which have received the name 

 of Enchondroma. (Figs. 308 and 

 309.) The microscopical cha- 

 racteristics of this change have 

 been described by the author 



come acquainted with the struc- 

 ture of teeth under the micro- 

 scope ; they are highly interest- 

 ing to the physiologist, and im- 

 portant guides to the naturalist 

 in the classification of animals. 

 Professor Owen has said, " If the 

 microscope is essential to the full 



nnrl trnp intprnrpffltinn nf thp Fi S- s06 - A vertical section of 



interpretation 01 tne carMag ^ wit h dusters of ceils 



Vegetable remains Of a former 



-ij... ,-| ! IT 



WOrld, it IS not leSS indispensable 



tO the investigator Of the fossi- 

 -. , f t -r> 



llSed parts OI animals. It has 



sometimes happened that a few 



Scattered teeth have been the 

 . j. ,. f, i -,./ 



only indications of animal life 

 throughout an extensive stratum ; and when these teeth 

 happened not to be characterised by any well-marked 

 peculiarity of external form, there remained no other 

 test by which their nature could be ascertained than that 

 of the microscopic examination of their intimate tissue. 

 By the microscope alone could the existence of Keuper- 



arranged in columns previous to 

 conversion into bone, which is 

 seen consolidated at the upper 

 surface. ^ greater opacity of 

 tnis po rtlon 1S owing to the m- 

 crease of osseous fibres, the opa- 



the dark intercellular spaces be- 

 come occupied by vessels. 



