72 VOICE AND SPEECH. 



ankle joint. As regards each of these parts, excepting the 

 head, the supporting muscles are aided by the forms of the 

 joints and the arrangement of the ligaments. In sitting, 

 the body if unsupported in front or behind is balanced on 

 the tubera isc/rii. 



- In walking, the position of the advancing or acting limb 

 at the beginning of each step, is represented by the vertical 

 side, the following limb by the hypothenuse of a right- 

 angled triangle, of which the base is a step or pace, and 

 the apex is in the position of the hip-joint : at the same 

 moment the knee and ankle joints are flexed. Towards 

 the end of each step, both joints become strongly extended. 

 During each step the pressure of the foot upon the ground 

 increases towards the end : the pelvis oscillates once from 

 side to side and twice up and down, for every two paces, i.e. 

 in each period of progression. In walking there is no 

 interval during which the weight of the body is unsup- 

 ported : in running an interval exists, the relative length 

 of which increases as the pace quickens. 



VOICE AND SPEECH. 



The movements of the thyroid and arytenoid cartilages 

 by which the form of the glottis and the tension of the 

 cords are modified, are, (i) rotation of the thyroid on its 

 horizontal axis ; (2) rotation of each arytenoid on its 

 vertical axis ; and (3) rotation of each arytenoid on its 

 horizontal axis. The first produces tightening or relax- 

 ation of the cords, the second, opening or closure of the 

 vocal glottis. By the third, the arytenoid cartilages are 

 approximated to or withdrawn from each other so as 

 to vary the width of the space between them. 



It is the principal function of the glottis to produce 

 those " compound musical tones " to which in physiology 

 we apply the term " voice." These, when modified by the 



