MO 



I NDULATORY FORCES. ACOUSTICS. 



[OKOAJTS OF VOICE. 



breath ; and by tho various conditions of the tongue, tho 

 palate, the teeth, the lips, according to the position in 

 which they happen to bo at the moment 



The chest ana lungs together constitute, in reference 

 to the voice, a musical bellows, capable of supplying air 

 with moro or less force to the organs of voice. The 

 peculiarity of these bellows is, that by them the air must 

 be r-nuwed at short intervals, entering from without 

 by the same passage by which it is expelled when the 

 voice U exercised. It can, however, supply air without 

 interruption, in a continued stream, for about fifteen 

 seconds. The lung consists of two large bags of air, 

 and does not materially differ from tho wind-box of an 

 organ, or rather from the bag of a bagpipe. No air can 

 enter the lung, or escape from it, except through the 

 windpipe. The walls of the chest are everywhere in 

 contact with the outer surface of the lung, and close in, 

 around the point at which tho windpipe rises upwards 

 to the larynx. The chest is capable of expansion in 

 every direction ; that in to say, by means of muscular 

 action its walls recede from the surface of tho lung, so 

 that the cavity in which this air-bag is contained, is 

 augmented in every direction in length, in breadth, in 

 depth. Whenever this enlargement commences, the air 

 begins to enter from without By this process, in two 

 or throe seconds, many cubic inches of air cau be drawn 

 into the lungs. So nice is the action of tho muscles, 

 by which the chest is again contracted in size, and the 

 lung is compressed, that the stream of air which shall 

 issue in a given period through the larynx, by the in- 

 fluence of the will, is under the moat complete control. 

 The prominence of the larynx on the fore part of the 

 neck, is popularly known by the name of Adam's apple ; 

 by which, probably, its remarkably greater prominence 

 in tho male than in the female, is referred to. The long 

 succession of minute tubes, by the gradual union of 

 which the other trunks, and, finally, the windpipe, are 

 formed, has this peculiarity that the aggregate of the 

 areas of tho smaller tubes greatly exceeds the area of 

 the trunks which they combine to form. From tho 

 windpipe throughout, almost to their origin in the 

 minute cells, the tubes are provided with tonse walls, by 

 means of the cartilaginous appendages before referred 

 to ; in tho windpipe itself these cartilages assuming a 



lucre definite form. They 

 are in complete rings of 

 cartilage, being deficient 

 posteriorly; that is, each 

 ring of tho windpipe tra- 

 verses about two-thirds of 

 its circumference, leaving 

 the remaining one-third, on 

 its posterior aspect, desti- 

 tute of this support. The 

 number of rings in the 

 windpipe is from fifteen to 

 twenty; in other respects 

 the tube is chiefly mem- 

 branous, yet provided with 

 muscular fibres capable of 

 diminishing its calibre, by 

 drawing together the extre- 

 mities of the rings. It has 

 been proved, by sufficient 

 experiments, that when the 

 larynx is raised by the 

 powerful muscles attached 

 to it, the windpipe is drawn 

 up from tho chest in a cor- 

 responding extent, and that at the same time its dia- 

 meter is diminished by about one-third. 



Tho base, or lowest part of the larynx, rests on the 

 upper part of the windpipe (Fig. 12) ; and this base con- 

 sists of a ring, somewhat more developed than any of the 

 rings of the windpipe, yet not so different from those 

 but that it might bo regarded as tho summit of that 

 tube. This ring differs from the rings of the wind- 

 pipe in being complete all round ; it is not, however, 

 of a uniform breadth in the direction of from below 



Tig. U. 



, bu*ment or erleoid cartilage, 

 reatingon the cylindrical unil- 

 pipe ; , protecting cartilage or 

 thrrold cartilage; rf, valre-like 

 cartilage or epiglottis. 



Fig. . 



c. r> i viiiilal or m 

 cartilages; a. cricojd or lue- 

 !):(!;. ( irtilatfe ; e r, the 

 ton iru r or proper vocal 

 railed aUorocal liga- 

 ment* ; also arytonolheroid 

 ..r vocai 



livamrnu; //, the Trntii- 

 clea of the larynx ; </, the 

 epiglottis. 



upwards, being broader at the posterior part. 

 be likened, then, to a ring, with a stone or 

 the expansion behind cor- 

 responding to tho stone or 

 seal On the upper edge of 

 the expanded portion of 

 ring, at the base of the larynx, 

 are set two slender bodies of 

 a pyramidal form, which War 

 the most important part in 

 the mechanism of tho larynx 

 as an organ of voice. These 

 two bodies are exactly alike, 

 and are placed almost close 

 together, like two miniature 

 obelisks set on end. The con- 

 nection of their inferior extre- 

 mities with the basement ring 

 of the larynx, is by articula- 

 tion viz., by a true joint, 

 like the shoulder-joint; that 

 is to say, they are movable on 

 the cartilaginous ring which sup- 

 ports them. From the one to the 

 other, on their posterior aspect, 

 muscular fibres extend, by the contraction of which, these 

 two minute pyramids are made to approximate together. 

 From the fore part of each, near their bases, an elastic sub- 

 stance proceeds forwards, converging, to interlace with its 

 fellow at the anterior part of the larynx ; that is to say, 

 a minute, somewhat triangular, space is fonned by two 

 portions of elastic tissue, which cross the basement ring 

 of the larynx from behind forwards, the base of this 

 triangle being the space between tho two pyramidal bodies 

 just spoken of and its apex behind a portion of tho 

 larynx to be presently alluded to. This triangular space 

 between these two portions of tissue, or vocal ligaments, 

 as they are called, is the aperture by which tho breath 

 enters and issues in respiration, and by which, when 

 contracted to a narrow chink, the air is forced through 

 in the exercise of voice. (See Fig. 13). These, then, are 

 the most essential parts of the larynx ; tho two pyra- 

 midal bodies each resting on tho posterior part of tho 

 basement ring, while the two ligaments proceed forwards, 

 each from the base of one of these pyramids, to form a 

 triangle, the apex of which is so directed as to be mi r 

 the anterior part of the aperture of that basement ring. 

 It is manifest, that when these two minute pyramids are 

 drawn close together by the action of the muscular 

 fibres, the base of the triangular opening is dimini 

 so that tho posterior, or wider part of tho opening, In- 

 comes obliterated ; also, if the apex of this triang! 

 drawn forwards, that the sides formed by the two vocal 

 ligaments will still further approximate. Such, then, 

 are tho two actions by which tho triangular aperture is 

 reduced to a minute chink namely, by the points to 

 which its base is attached being made to approximate, 

 and its apex being drawn forwards. 



Other muscular fibres are so disposed as to antagonise 

 the forces which close the aperture ; two sets of fibres on 

 side extend from tho basement ring inwards, to be 

 attached to tho pyramidal cartilages, by which they are 

 drawn asunder, and tho base of their rectangular aper- 

 ture again restored to its former extent. 



Several important, yet less esseutml parts of the larynx, 

 remain to be described. The anterior narrow part of 

 the basement ring supports that great prominence w 

 constitutes Adam's apple. This is by far the largest 

 portion of tho larynx, but may be regarded merely as a 

 defensive plate guarding tho essential parts of the organ 

 from injury. When tho finger is placed upon its upper 

 margin, and directed a little upwards, a hard, wire like 

 circle is felt ; this is the convexity of the hyoid bone, or 

 bone of the tongue, which has intimate is, by 



ligaments and muscular fibres, with many adjacent parts, 

 so that it is rendered, as it were, a centre of motion. 

 Hence, when the hyoid bone is raised, many of tlie. adja- 

 cent parts follow its movements. Tho hyoid bone is 

 described as having tho shape of the Greek upsilon, the 



