44 APHORISMS ON THE FRONTAL SINUSES. 



common gradation of their growth is determinate, and the excep- 

 tions to it are not more numerous or important than those excep- 

 tions which prove a general rule in any of the sciences or philoso- 

 phy. By the tenth year, their horizontal diameter is scarcely half 

 a line ; by the Jlfteenih year, it seldom exceeds one line ; by the 

 trveniieth, it is rarely one line and a half; by the fortieth, it ap- 

 proaches occasionally to two lines ; and after the fiftieth year of 

 man's life, it is about ttvo lines and a half in extent. 



V. The Frontal Cavities result from a natural process ; but the 

 causes of their formation, and its mode, remain among the deside- 

 rates of physiology. They depend apparently on simple absorption 

 of the interosseous cellular texture ; and with the progress of this 

 absortion their dimensions increase. Not till life's decline does the 

 internal plate of the bone recede inwards. It is quite improbable that 

 the external table of the skull ever advances : were such a process 

 certain, it would establish an anomaly from the regular order of 

 organization. 



VI. The Frontal Sinuses may be wide, and their depth, never., 

 theless, not more than was that of the bone's primitive cellular 

 Structure. Their horizontal diameter may be one line ; and, at the 

 same time, that of the frontal bone itself, naturally, not more than 

 two. Wherefore, the childish practice of poking these broad but 

 shallow holes, from underneath, with a bit of wire, can never re- 

 veal the true distance of the bone's external surface from the brain. 

 Finally, here, the deepness of these cavities may be, and often is, 

 augmented by disease ; and they have this much to do with old age 

 that their greatest enlargement and old age are concomitant. 



VII. Phrenologists admit that the Frontal Sinuses interfere with 

 those parts of the skull which indicate the relative proportions of 

 the organs of some of the perceptive intellectual faculties. This is 

 the course after which the growth of these cavities usually proceeds. 

 First of all, organic absorption gradually removes the cellular texture 

 from between the tables of the frontal bone where it covers the or- 

 gan of Individuality. Next, this absorption extends to the region of 

 Size ; then to that of Form ; and then, in mature age, to that of 

 Weight and the lower angle of Locality. Rarely, indeed, does it pass 

 these limits of length and breadth, except in declining life and disease. 



