LARYNX AND PHONATION. 



347 



kind. " We believe that the great sympathetic system is not 

 simply a vaso-motor nerve ; it has a direct influence on 

 calorification, its essential office being the regulation of tho 

 chemico-physical phenomena whigh take place in the tissues, 

 when these enter into conflict with the blood by means of 

 the capillary circulation." He holds that this nerve acts as 

 a constant check upon the circulation, and also serves to 

 modify the oxidation that goes on in the tissues as well as the 

 decompositions which produce heat ; producing, after section 

 of the sympathetic, an increase of vascularization and calori- 

 fication, both of which phenomena are entirely local. 



III. OF THE LARYNX AND PHONATION. 



As we shall presently find that the external integuments 

 are modified in certain parts, for the purpose of more readily 

 receiving the impressions made by the external world, thus 

 constituting the organs of the senses, so we shall find that the 

 air-bearing respiratory tube exhibits in the upper part of the 

 neck a special arrangement, constituting the larynx, an organ 

 which places man in relation with the outer world, and 

 especially with his kind. This organ is one of the most 

 important of those which serve the purposes 

 of animal life (fonctions de relation), form- 

 ing, as it does, our principal means of com- 

 munication, in fact, of expression. 



The other organs of communication and 

 expression are scattered throughout the 

 various external organs: thus the limbs, es- 

 pecially the arms, are organs for expression, 

 the signs of which are generally easily under- 

 stood. The muscular system of the face 

 forms a special organ of expression ; all 

 these muscles, with the exception of those of 

 the globe of the eye, are innervated by the 

 facial nerve of the seventh pair, which is 

 under the control of the medulla oblongata / 

 thus the thousand varieties of expression 

 presented by the face may be produced by a simple reflex 

 action, without any participation of the will. 



* The laryngeal part of the air-passage presents three circumscribed aper- 

 tures or embrasures: 1, in the aryteno-epiglottidean folds; 2, iu the imper vocal 

 cords ; 3, in the lower vocal cords. V,V, Ventricles of the larynx. T, Trachea- 



Fig. 84. Diagram 

 of vertical section 

 of the larynx.* 



