AMAUttOSIS AND ATROPHY OF THE EYES. 125 



manner of their formation. He says (" Principles and 

 Practice of Veterinary Surgery," p. 412) : 



" Cysts containing teeth have been found in the tes- 

 ticles and other parts of the body, but those which are 

 of importance to practical men are found within the 

 antrum. I have seen several cases of this kind, and 

 have extracted teeth from cysts even so high as the 

 base of the ear. 



"During life these tumors are distinguishable by 

 more or less disfigurement of the face, by a bulging out 

 of the superior maxillary bone, accompanied in some 

 cases by amaurosis of one eye, succeeded by atrophy 

 of the eye from the pressure of the growing tumor. 

 In other cases these complications are not present, but 

 now and then an abscess forms in the post-orbital re- 

 gion, which will be found on examination to contain a 

 hard body an imperfect tooth. 



" To understand the process by which these tumors 

 are formed, it is necessary to remember that the teeth 

 of all animals belong to and arise from the membran- 

 ous portion of the digestive canal, and that at a very 

 early period of fetal life a provision is made for the 

 development of the permanent teeth as well as the 

 temporary. This provision, according to Goodsir, is 

 as follows : ' As early as the sixth week of intra-uteral 

 life (human), a groove appears along the border of the 

 future jaws, called the primitive dental groove, which 

 is lined by the membrane of the mouth. At the bot- 

 tom of this groove projections papillae spring up, 

 corresponding in number with the temporary teeth. 

 While the growth of the papillae is going on, partitions 

 are formed across the grooves, by which they become 

 separated from, each other. These partitions subse- 



