344 



ANATOMY AND PHYSIOLOGY 



direction. This condition is called squint or strabismus, or "cross-eye." 

 It oftenest happens with either the internal or external rectus. 



The muscles of the iris and the ciliary body are the ocular 

 muscles. 



Associated movements are of interest in connection with the 

 eye. The central connections are so arranged that the external 

 rectus of one eye moves with the internal rectus of the other; 

 the internal recti of the two eyes act together when they are 

 directed toward a near object. The act of convergence is asso- 

 ciated with contraction of the pupil and ac- 

 commodation. It is easily understood that 

 fixing the eye upon a near object is not a 

 simple act : the circular fibers of the iris, 

 the ciliary muscle and the internal recti are 

 all called into action. (The far-sighted eye 

 is doing this work constantly; it is there- 

 fore important to reh'eve this strain of 

 overwork by well-fitted lenses.) 



FIG. 223. INTERIOR OF 

 LARYNX (LEFT SIDE RE- 

 MOVED). (Sappey.) 



2, Epiglottis; 5, so-called 

 "false vocal cord"; 9, vocal 

 band; 13, thyroid cartilage; 

 14, arytenoid cartilage. 

 The other figures refer to 

 parts not mentioned in the 

 text. 



THE VOICE 



The voice, by which we establish most 

 frequent communication with the outside 

 world, is a special endowment for the ex- 

 pression of ideas awakened in conscious- 

 ness by the senses. It is therefore not 

 inappropriately considered in this con- 

 nection. 



The larynx is the organ of the voice. 



(The larynx, lips, tongue and teeth are the organs of speech.} 

 A brief description of the larynx is given on page 234, of tongue 

 and teeth, pp. 132, 35. 



The structures which are specially concerned in the production 

 of the voice, in addition to the cartilages described, are the 

 vocal bands (also known as vocal cords, and true vocal cords}. 

 These are stretched across the larynx from front to back, being 

 attached to the thyroid cartilage anteriorly and the two arytenoid 

 cartilages posteriorly, thus dividing the cavity into upper and lower 

 portions (Fig. 223). 



