86 Dr Stone on the Frmital Sinus. 



In confirmation of this view, numerous facts present them- 

 selves, which are of a positive, not of a negative character : — 



I. I may refer to the period of life when these sinuses become 

 developed, for although it has been asserted by a celebrated cranial 

 theorist, that the sinuses do not exist in young persons, but only 

 in old persons, or after chronic insanity, yet this assertion is con- 

 trary to all previous authority, and opposed to the most direct 

 evidence of Nature. Eyssonuius, Coiterus, Fallopius, Riolan, 

 Vidus Vidian, Bartholin, Ruysch, Duverney, Portal, Bertin, 

 Sabatier, Bichat, and others, state the non-existence of these si- 

 nuses in infants, but describe them as occurring about puberty ; 

 and the latter, especially, attributing their expansion to its pro- 

 per cause, viz. the development of the external table of the 

 skull, states that they can only be formed at that period 

 when this development takes place, which, as we have seen, 

 commences after seven years of age. The anatomy, too, of 

 the inferior animals refutes, it would appear, the asseveration, 

 for Cuvier remarks, " Cest une regie generale pour tous 

 les carnassiers, ils (les sinus frontaux) ne prennent leur deve- 

 lopement qu'avec age *.'"* 



II. Every sinus is lined with a mucous membrane, a fact 

 known to the earliest anatomists who paid attention to this sub- 

 ject ; and here it may be remarked, that when, owing to any 

 impediment, such as the narrowness of the nasal passage, this 

 mucous membrane has not been able to extend between the cra- 

 nial tables, then the sinus does not exist, and its place is supplied 

 by a deposition of bony diploe, which now meeting with no ob- 

 stacle, is freely deposited, and occupies what would otherwise 

 have been the space of the frontal sinus. This view satisfacto- 

 rily explains the observation of the present Dr Monro, who, 

 alluding to crania without these frontal sinuses, remarks, that" in 

 such cases the tables are as far separated as if the sinuses exist- 

 ed, for their place in this case is tilled up with diploe •f.'" 



III. It has been shewn that the average increase in the 

 growth of the head, when its longitudinal gains on its trans- 

 verse dimension, which is entirely owing to the development be- 

 fore the meatus, is ^qI\\% of an inch, which I found, subsequent- 



• Cuvier, Recherches sur les Ossemens Fossils, torn. iv. p. 358. 

 •f Monro, Elements of Anatomy, vol. i. p. 134. 



