: 
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23 
The physiological aspect of speech must now be considered, inas- 
much as there are many psychologists who profess that animals do not 
articulate solely from lack of the necessary mechanism and not from 
any deficiency in mental powers. The investigations of the eminent 
biologist, M. Paul Broca, tend to localise the faculty of speech in a very 
circumscribed area, more especially of the left cerebral hemisphere of 
the brain. The organ occurs on the upper edge of what is termed the 
“Sylvian fissure ” opposite the “so-called island of Reil ” in the posterior 
half of the third frontal convolutions of the right or left hemisphere. 
On the right side it is but feebly developed, but any lesion or disease of 
“‘ Broca’s organ” on the left side is frequently accompanied by inability 
to use words rightly and aphasia, or entire loss of speech. The power 
of making appropriate gestures or sign language remained unaffected 
in as many as eleven out of sixteen cases recently noted. The mechan- 
ism of voice and of articulation really depends on two essentials, air and 
muscle. The rhythmical contraction of the diaphragm, a muscular 
plate separating the thoraic from the visceral cavity, with the mobility 
of the lower ribs, draw into the lungs the air necessary for existence. 
The forcible contractions of the muscular cellular lung tissues expel 
the returning current, and it is chiefly by means of the air thus 
breathed out from the lungs that tone and resonance are produced at 
will ; therefore we use our spent breath in speaking, and do not really 
waste it even in the most futile argument. The expired air passes 
silently out through the upper windpipe, into a box-like prolongation 
of the upper gullet called the larynx, whenever the passage is un- 
obstructed. The voluntary erection of the two movable membranous 
half-valves of which the free edges form the vocal chords and are 
‘stretched tense, relaxed or shifted by the laryngeal cartilages, causes 
the returning air wave to pass through the narrow fissure (the glottis) 
-so formed, and sets the vocal chords vibrating. The tone thus produced 
asses on, either through the nasal cavity, or, if that is already closed, 
y the muscular elevation of the soft palate, it escapes freely into the 
mouth cavity in vowel vibrations, if the jaws be wide open, or is 
differentiated into consonants by the varying degrees of mouth clcsure, 
the movement of the lower jaw, contraction of the lips, and of the 
glottis, the elevation and depression of the palatal cavity, and the 
movements of the tongue. It depends, therefore, entirely on the soft 
palate, which is largely concerned with the production of vowels, 
whether the sound be a nasal resonant or produced through the mouth. 
‘The larynx is the chief tone-producing organ. It can be elevated and 
depressed, and is entirely supported in the cavity of the gullet by the 
“vu” or horse-shoeshaped bones and cartilages (0s hyoides), to which 
some of the muscles of the tongue and palate are attached. This 
hyoid arch is suspended by ligaments fixed to the upper jaw of 
the skull. It has also important muscular attachments to the 
inner edge of the point of union (or symphisis) of the two rami 
of the lower jaw and to the sternum and the inner edges of 
the shoulder blade. In fact, the hyoid is the mainspring of articula- 
tion, and the degrees of ossification of the central cartilages of the arch 
increase with middle life, and become completelv ossified in old age 
among the European races, a result which has been attributed to 
