34 The Microscope. 



Doubtless every physician has asked himself the question 

 when a patient has applied to him to relieve an aching tooth, 

 Why cannot the enamel of the tooth be replaced by repair or 

 growth as bone or other tissues ? Every surgeon amputates a 

 limb with the assurance that the end of the bone will heal over. 

 The fractured limb will unite under proper treatment, and co- 

 aptation of the parts, or in other words the separation of the 

 continuity in bone will be replaced by new bone, but when the 

 enamel of a tooth has been fractured or destroyed the reparntive 

 process is wholly wanting, and unless some arlificial process is 

 resorted to the wound increases until the tooth or its usefulness 

 is destroyed. 



Close as the analogy may appear to the casual observer, a wide 

 disparity is seen to exist when we study the origin, development 

 and appearance of each in detail, and it is only when we have 

 followed out this, that we can give nny valid reasons which will 

 answer the foregoing question. 



From a few human embryos, and also from several small ani- 

 mals, I have mounted many hundred sections of bone and of 

 the inferior maxilla which, when contrasted have suggested the 

 theme of this paper. These embryos had been preserved in or- 

 dinary alcohol, some of them for several years. The part which 

 I wished to study, as for instance the lower jaw, was carefully 

 dissected out by cutting from the angle of the mouth through 

 the cheek directly back to the ramus and disarticulating from 

 the temporal bone, then dividing at the symphysis mentis and 

 removing the tongue; each part was placed in borax-carmine 

 staining fluid for twenty-four hours, then into the discharging 

 fluid for twenty-four hours, after which the specimen was treated 

 with each of the following for l.venty-four hours, successively: 

 alcohol 95 })er cent., alcohol absolute and chloroform ; after 

 this it was transferred to paraffin kept at the temperature 

 of from 115° F. to 125° F. for six hours, then after suddenly cool- 

 ing the paraffin with the specimen within, it was transferred to 

 the microtome and sectioned as desired. By using care in trim- 

 ming the paraffin close to the specimen and in such a way that 

 a section across the top would be a small square I have succeed- 

 ed in mounting from sixty to eighty consecutive sections under 

 one f inch cover glass. The mounting was done as follows. 



The size and position of the cover glass in relation to the slide 



