2 SUPERFICIAL ANATOMY OF THE HEAD AND NECK. 



two frontal, and backwards to that between the two parietal bones ; the latter 

 interval conducts to the triradiate posterior fontanelle, the lateral limbs of which 

 are continued downwards along the upper margins of the occipital bone. 



Fig. 1. FRONT VIEW OF SKULL, SHOWING EXTENT OF CEREBRUM, AIR-SPACES, EXIT OF NERVES, &c. f 



(G. D. T.) 



The outline of the cerebrum is shown in reel, and the position of the superior longitudinal sinus in 

 blue. The frontal sinus with the infundibulum and the maxillary antrum are indicated by patches of 

 shading, and the nasal duct with the lachrymal sac by a dotted line. The following letters refer to the 

 nerves : s o, supraorbital ; s T, supratrochlear ; i T, infratrochlear ; L, lachrymal ; N, nasal ; i o, infra- 

 orbital ; M a, malar ; B, buccal ; M e, mental. 



The frontal sinuses are contained in the lower part of the frontal bone, above 

 the root of the nose and the inner ends of the eyebrows. In extent and capacity 

 they vary greatly in different individuals ; as a rule they are larger in the male 

 than in the female, and are absent before the seventh year of life. In the adult 



