352 MAMMALIAN ANATOMY 







VARIATIONS IN FORM AND DEVELOPMENT. 



The maxillary presents few and unimportant variations in form. 

 The external surface of the body under the malar process is sometimes 

 much reduced in height ; the canine eminence varies in prominence ; 

 the lachrymal tubercle may be absent ; the nasal surface of the nasal 

 process exhibits variable markings for the attachment of the lateral 

 ethmoid. 



The infraorbital foramen may be large or small, round or oval. 

 It is not infrequently double; of two hundred and fifty maxillaries 

 examined it was double in twenty, or twelve and a half per cent. 

 This variation is often, but not invariably, symmetrical. 



The alveolar border exhibits variations in the number of sockets 

 for the teeth. 



One hundred maxillaries (rights and lefts) were studied with refer- 

 ence to this point, with the following results : 



The canine alveolus presented no variations. 



The first premolar was entirely absent in nineteen ; was indicated 

 by one alveolus in forty -three ; by two separate alveoli in nine ; and 

 by two more or less confluent alveoli in twenty-nine. 



The second premolar had two alveoli in eighty-seven ; three in 

 nine ; and three with the third or internal more or less confluent 

 with the outer posterior, in four. 



The third premolar was always implanted in three alveoli. 



The small molar was absent in five maxillaries ; showed one 

 alveolus in twenty-one ; two alveoli in thirty-one ; and two more or 

 less confluent in forty-three. 



The following table exhibits the manner in which these variations 

 occurred together. The first figure in each case represents the number 

 of alveoli for the first premolar ; the second figure, the number for the 

 second premolar, and the third figure, the number for the molar. 

 Confluence (C) in the cases of the first premolar and the molar is 

 between the two alveoli when present, in the case of the second 

 premolar between the abnormal third alveolus and the normal pos- 

 terior outer alveolus. The figure followino- the dash is the number of 



O O 



times the combination was found in one hundred maxillaries. Thus 

 1, 2, C, 12 means that in twelve specimens the first premolar had 

 one alveolus ; the second premolar two ; and the molar two, more or 

 less confluent. 



