28 



PROF. B. C. A. WINDLE AND MR. J. HUMPHREYS [Jail. 14, 



space existing between neighbours in less roomy jaws. In still 

 further shortening a torsion of certain teeth in the upper jaw takes 

 place which always follows a very definite course. 



The tooth first to feel the strain in every case with which we have 

 met is the third upper premolar, which becomes slightly obhque and 

 then is rotated until it lies transversely across instead of along the 

 alveolar border. The next tooth to yield is the second premolar, 

 which is sometimes slightly oblique, the third being transverse and 

 sometimes in further advanced cases also rotated into a transverse 

 position. The teeth of the lower jaw exhiljit no such transverse 

 rotation. In the Bull-dog shortening does not proceed so far in 

 the lower as in the upper, and consequently the upper canine has 

 for its lower antagonists one or more of the premolars. Thus, in 

 six Bull-dogs' skulls in which we noted the position the upper 

 canine three times was over Pm. 3, twice between Pi^iTii and Pm. 3, and 

 once over Pm. 2. 



In other cases the pressure for space may carry the last lower 

 molar up on to the ramus of the jaw. Sometimes tlie lower jaws, 

 instead of being nearly straight, are distinctly bowed to accommodate 

 themselves to the curve of the teeth in the upper jaw. The following 

 table shows the torsion of premolars in certain cases where it was 

 well marked. 



Table XXXVI. — Torsion of Premolars. 



