EXTRACT L.A. 



ON THE "PNEUMATIC SPACES" OF THE HEAD AND 

 FACE, AND THE OLFACTORY NERVES AND MUCOSA. 



THE anatomy and physiology of the pneumatic spaces,, 

 so called, and the olfactory apparatus lie at the foundation 

 of this series of studies. 



It appears to us that the pneumatic spaces, so called, 

 of the head and face fulfil : first^ a mechanical purpose 

 by lightening the osseous structures of the facial and 

 cephalic skeleton ; second, they render more yielding the 

 floor of the skull and points of entrance and exit of the 

 cephalic nerves and blood-vessels ; third^ they give facilities 

 for the conduction and modulation of sound ; and/0#r/^, 

 they minimise the effects of shock or concussion on the 

 cephalic contents by affording, so to speak, an air-cushioned 

 chamber for their safe lodgment. In this connection they 

 may also be said to afford a means of modifying and 

 mellowing the quality and tone of the voice making it 

 more or less cavernous, sonorous, or in reality antral. 



Amongst the physiological functions subserved by them 

 may be enumerated the following, viz. a surface, for the 

 chemical interchange, or exit and entrance, of gases or 

 liquids, which may leave it or become vapourised and 

 join the air currents in the nasal-pharyngeal cavities, thus 

 providing a subsidiary breathing apparatus, as it were, for 

 the head, face, and neck ; so that, when the contents of 

 the cephalic cavity cannot be sufficiently aerated and 

 purified through the ordinary channels of exit and 

 entrance, a safety valve is thus provided, or opened, 

 and a supplemental oxygenating agency supplied to 



