GENERAL SCIENCE 



t 



the stimulus of directing those activities in which the hands are em- 

 ployed, and of those reactions which result from expression of thought 

 through hand work. 



THE MOUTH 



The cavity known as the mouth is not only the beginning 

 of the digestive canal, but it is one of the chief organs of 

 speech. In Physics from the study ^of 

 sound we learn something of the uses of 

 the mouth and its adjacent parts in talk- 

 ing and in singing. Complete control of 

 the muscular parts of the mouth and its 

 connected cavities is necessary to a singer 

 in order to give utterance to sounds in their 

 proper relationship in the musical scale. 



Just above the larynx, and embedded 

 in the tissues, there may be felt on either 

 side of the neck the small semi-elliptical 

 hyoid bone. From it many of the mus- 

 cular fibres of the tongue arise. It does 

 not connect with other bones of the 



< ,1 i T 



skeleton the only case of the kind in 



^ Q body. As a movable bdS6 it gives 



to the tongue an exceedingly wide range 

 of movement. Back of the mouth cavity and the at- 

 tached end of the 'tongue is another cavity with muscular 

 walls known as the pharynx (far'-inks). This is the upper 

 enlarged extremity of the muscular food tube, or oesophagus, 

 which leads to the stomach. Food and drink, when forced 

 by the tongue back into the pharynx, pass over the glottis, 

 or entrance to the larynx, and are kept from getting into 

 it by a cartilaginous cover known as the epiglottis. Cough- 

 ing, strangling, and choking mark spasmodic efforts to dis- 

 lodge food or drink that gets into the glottis. Once within 



FIG. 2. Hyoid 

 bone, h\ trachea, t; 

 bronchi, b, b'\ larynx, 

 I; glottis, g. 



