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the promontary is developed, the round hole is directed outwards ; 

 but, in proportion as its growth advances, it conceals this hole and 

 directs it backwards. When the mastoid process develops itself, it 

 occasions a new direction in the hole, which it turns again more out- 

 wards. 



My observations on this subject agree with those of the illustrious 

 Scarpa, so far as relates to the varieties, which we find in the 

 direction of this hole in different individuals ; but, I am fully of 

 opinion, with Bichat and Buisson, that it is very difficult to trace 

 any connexion between its aspect and the age of the subject. 

 I have indeed, in my collection, preparations, which prove, that, 

 in almost any two subjects of similar age, the aspect will not be 

 found the same. While, in some cases, we shall find it pos- 

 sessed of the same direction, in preparations taken from subjects of 

 very dissimilar ages, it will exhibit, in others, a diflferent aspect, 

 although they be of the same age. Whether the direction of this 

 hole depends on the development of the promontory and mastoid 

 proces is not easy to determine ; but, if it is they which influence 

 it, we ought to be prepared to expect much diversity; for the exact 

 manner, in which they grow, is subject to considerable variety. 



The promontory is visible about the third month after conception, 

 and, in the fourth, it is ossified. It does not grow so quickly as 

 the oval and round holes, which are above and below it ; hence 

 it has not attained its full size, till some time after birth ; but it 

 is developed with more rapidity than the cavity of the tympanum, into 

 which it projects ; and, therefore, about the fourth month after 

 conception, it is in contact with the membrane of the tympanum. 

 When we compare the promontory of a foetus, at the ninth month, 

 with the same part in the adult, they appear to differ, not so much in 

 magnitude as structure. In the foetus, it is porous and spongy; ut, 



