430 SIMPLE TUMOUHS. 



secure it Ly metallic suture. When the wound is healed, it will 

 be found that the discharge from the nose and the difficulty in 

 breathing have disappeared, and that the life of a valuable young 

 animal has been saved. 



DENTIGEROUS CYSTS OR TEETH TUMOURS. 



Cysts containing teeth have been found m the testicles and 

 other parts of the body ; but the teeth-bearing cysts, which are 

 of importance to practical men, are those immense collections of 

 imperfect teeth-forming tumours within tlie antrum, as shown 

 in Photo-lithograph, Plate II., Pig. 9. I have met several cases 

 of this kind, and have extracted teeth from even so high as the 

 base of the ear. 



During life, these tumoiirs are distinguishable by more or less 

 disfigurement of the face, by a bulging outwards 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 tumour. In other cases, these complications are not 

 present, but now and then an abscess forms in the post-orbital 

 region, which will be found upon examination to contain a hard 

 body — an imperfect tooth. 



To understand the process by which these " teeth tumours '* 

 are formed, it will be necessary to remember that the teeth of 

 all animals belong to and arise from the membraneous portion 

 of the digestive canal, and that at a very early period of fcetal 

 life a provision is made for the development of the permanent 

 teeth, as well as for that of the temporary ones. This provi- 

 sion, according to Goodsir, who devoted much attention to the 

 subject, is as follows : — As early as the sixth week of intra- 

 uteral life (in the human foetus) 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 bottom 

 of this groove projections — papillae — spring up, corresponding 

 in number with the temporary teeth ; these gradually increase in 

 size, and acquire the shape of the future teeth. 



Whilst the growth of the papillae is going on, partitions are 

 formed across the groove, by which they become separated 

 from each other. These partitions subsequently form the bony 

 sockets. 



