2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.67 



here concern ns, for any resulting asymmetry will be purely me- 

 chanical, affecting only the immediate portion injured, and probably 

 having no appreciable effect whatever upon other portions of the 

 skull. That this premise is founded on fact is shown by a skull of 

 TJrsus eltonclarJci (No. 232382, Biological Survey collection) from 

 Chichagof Island, Alaska. This is of an adult whose entire right 

 coronoid process is missing. The bone healed well, proving that the 

 injury antedated the death of the animal by a considerable period. 

 Had this happened during the youth of the animal, the practical de- 

 struction of function of the right temporal muscle would have re- 

 sulted in profound cranial changes, but there is now not the slightest 

 asymmetry. 



Attention should here be called to the study by Hollister^ of 

 the skulls of captive lions. In this it is aigued that certain condi- 

 tions — notably massiveness — to be met with in the skulls of lions 

 raised in captivity are the result of myological stimuli, the muscles 

 being effected by conditions brought to bear during captivity. If 

 this be the case, then the criteria usually employed for judging the 

 strength of a skull and its musculature must be altered. A thorough 

 examination of Hollister's material- by the present writer, however, 

 has produced new evidence and led him to the conclusion that the 

 conditions obtaining in the skulls of these captives are pathological 

 rather than myological. 



PubUshed references to asymmetrical skulls of mammals other 

 than man include an experiment conducted by Anthony,^ in the 

 course of which he cut the left temporal muscle of a puppy upon the 

 day of its birth. The dog, killed by accident when something less 

 than one year old, showed marked atrophy of one temporal muscle, 

 even in life; but the only really definite asymmetry to be noted in 

 the skull is the absence upon the left side of the ridge which normally 

 marks the medial boundary of the origin of the temporal muscle. 

 The left, or "abnormal," zygomatic arch, as compared to the right, 

 is less than 1 mm. deeper, less than 3 closer to the cranium, and is 

 practically the same in length. The latter points are of interest as 

 showing the trend of the abnormal side, but the differences are too 

 slight to be of much significance in the present study. 



The same investigator, as senior author,^ experimented upon two 

 more dogs at a later date, with results that duplicated his first 

 efforts. 



1 Hollister, N., Some effects of environment and habit on captive lions, Proc. U. S. Nat. Mus., vol. 53, 

 1917, pp. 177-193. 



s Howell, A. B., Pathologic skulls of captive lions, Journ. Mamm., vol. 6, 1925, pp. 163-168. 



' Anthony, M. R., Introduction a I'fitude expfirimentale de la morphogfinie. Bull, et Mems. See. Anthr. 

 Paris, 1903, no. 2, pp. 119-145. 



< Anthony, M. R., et Pietkiewicz, W. B., Nouvelles experiences sur le role du muscle crotophyte dans 

 la constitution morphologique du crSne de la face, Compt. Rend. Acad. Sei., vol. 149, 1909, p. 870. 



