OUR FACE FROM FISH TO MAN 



the very jaw muscles in which its upper end was 

 embedded. In other cases when a muscle mass 

 becomes subjected repeatedly to new pressures or 

 friction across its line of action the surrounding 



/^U/t'SA 

 (CAV/TV OF MENISCUS) 



on "P^^^iJ'^fifs- """ ^^^C- 



COA/DYIE 

 OF JAW^ 



■GOMALE 



Fig. 22. Ohigin op the Interarticular Disc, or Meniscus, Lying 



Between the Lower Jaw and Its Socket in the 



Skull. (After Gaupp.) 



membranes give rise to a cushion or sac of con- 

 nective tissue filled with a clear liquid, which 

 serves to prevent the opposing surfaces from 

 grinding against each other. In an early embryo 

 (Fig. 22) of a primitive mammal (Perameles) 

 Professor E. Gaupp, the eminent comparative 



anatomist of Fribourg, found that a part of one 



38 



