68 THE TONER LECTURES. 



foramen iu adult life are by no means infrequent. In fourteen 

 skulls of Esquimaux examined eight showed the tympanic foramen 

 of defect. I have never seen the foramen in a Sandwich Island or 

 Tahitc cranium. Extended examinations might show variable per- 

 centage of occurrences in the different races. That the foramina 

 are factors in the distribution of pus in peri-meatal abscesses there 

 can be no doubt. 



The oval foramina of the sphenoid bone are often unequal in 

 size and of different shapes. The form may be so slightly changed 

 from the circular that the term oval is scarcely applicable to it. 

 This is often seen in Esquimaux crania. The rounded shape is 

 frequently found associated with the short skull and the oval form 

 with the long skull. When an asymmetry of the openings exists it 

 is rational to entertain the opinion that the side of the skull w'hich 

 show^s the greater elongation is also the side which will relain the 

 most elliptical foramen. 



If the base of the skull were perfectly symmetrical the line of the 

 basio-cranial suture, produced outward to the right and left, should 

 intersect the oval foramina at a fixed point ; but, in fact, the inter- 

 section is variable. This is in part owing to the differences in the 

 shapes of the openings, as already noted, and in part to the torsion 

 of the anterior segment of the skull. (See page 18.) 



The carotid canals may be asymmetrical. The left canal, when 

 asymmetry is present, is ordinarily the smaller.^ 



The foramen lacerum medium may be entirely absent, as is the 

 rule with the lower animals. The union of the apex of the petrosal 

 element against the body of the sphenoid bone is more frequently 

 seen in long, narrow skulls than in others, but may be seen inde- 

 pendently of skull form. 



The foramina on the side of the skull are the familiar mastoid 

 and the alisphenoid foramina. The latter are infrequently present. 

 They are the orifices of small diploic veins which come to the sur- 



^ For good examples see 1548, Swede; 914, negro (A. N. S.). 



