294 DESIGN IN NATURE 



tion or relaxation of the diaphragmatic muscles, diminish the dimensions of the thorax in all its diameters. The 

 abdominal muscles named and the triangularis sterni are as directly connected with the pulling down and lowering 

 of the ribs and sternum as the minor pectorals, intercostals, levatores costarum and scaleni are connected with the 

 rucking up and raising of the ribs and sternum. 



Second. If the abdominal muscles and triangularis sterni are not muscles of expiration, then the whole onus of 

 respiration is thrown upon the so-called inspiratory muscles, which are required forcibly to extend the abdominal 

 muscles and to put the ribs and a great many other structures on the stretch to ensure an elastic recoil, which 

 recoil will, unaided and without direction and guidance, produce the important act of expiration. Elasticity, 

 which Ls a mere mechanical property, is, according to the mechanical school, made to take the place of a first or 

 prime motor. 



Expiration is quite as important an act as inspiration. In some senses it is the more important of the two. 



The expiratory act has to regulate with extraordinary nicety the amount of air passing through the glottis and 

 the vocal chords in the production of voice, and the marvellous inflexions of which the voice is capable. The regu- 

 lation of the strong and ever-varying blasts of air required for declamation, intoning, singing, whispering, &c., could 

 not possibly be left to the haphazard power exercised by elasticity. These air currents, momentarily changing in 

 volume and intensity, demand for their production and management a set of living, co-ordinated muscles with 

 dehcately adjusted associated movements. The highly specialised muscles required are found in the larynx, in the 

 thorax, and in the abdomen. It has been sought to explain half the movements of the glottis and vocal chords by 

 elasticity, but I hold strongly that the movements are largely vital throughout. They are too dehcate, and require 

 too much fine adjustment to be delegated to any form of elastic recoil. 



In the whole animal economy there are no more ticklish functions to be discharged than are performed by the 

 muscles of the glottis, vocal chords, chest, and abdomen. All the muscles in question are definitely co-ordinated 

 and move with the greatest exactitude. They move, moreover, as highly sensitive organs with a sensory and motor 

 nerve supply. Nothing is left to chance and very little to elasticity. 



The statements made by physiologists concerning the movements of the glottis and vocal chords are at once 

 conflicting and confusing. Thus Professor Austin FUnt, usually a very careful and exact writer, says of the glottis 

 in connection with voice : " A nearly passive organ, opening widely for the passage of air into the lungs (because the 

 inspiratory act has a tendency to draw its edges together), and entirely passive in expiration, has now become a sort 

 of musical instrument, presenting a slit with borders capable of accurate vibration. The approximation of the 

 posterior extremities of the vocal chords and their tension by the action of certain of the intrinsic muscles are accom- 

 pUshed just before the vocal effort is actually made. The glottis being thus prepared for the emission of a par- 

 ticular sound the expiratory muscles [it will be observed that the elastic theory of expiration is here discarded] force 

 air through the larynx with the required power. It seems wonderful how a carefully-trained voice can be modulated 

 and varied in all its qualities, including the intensity of vibration, which is so completely under control.'''' [Here again 

 the elastic mechanical theory is set aside.] 



He proceeds : " The power of the voice is simply due to the force of the expiratory act, which is regulated 

 chiefly by the antagonistic relations of the diaphragm and the abdominal muscles. From the fact that the 

 diaphragm, as an active inspiratory muscle, is exactly opposed to the muscles which have a tendency to push the 

 abdominal organs, with the diaphragm over them, into the thoracic cavity, and thus to diminish the pulmonary 

 capacity, the expiratory and inspiratory acts may be balanced so nicely that the most dehcate vocal vibrations can 

 be produced." ^ 



There is much that is contradictory and misleading in these statements. How, I would inquire, can the glottis be 

 nearly passive in inspiration and wholly passive in expiration ? How can the air in phonation be forced through the 

 larynx with the required power by the expiratory muscles if these muscles do not act vitally and as apart from mere 

 elasticity ? and how can the vibration of the vocal chords be " completely under control " unless the expiratory 

 muscles and the muscles of the larynx which regulate the vibration are also under control ? How can " the antago- 

 nistic relations of the diaphragm and the abdominal muscles " adjust the expiratory act and the power of the voice ? 

 Why should the diaphragm be an active inspiratory muscle, and a passive expiratory one, exactly opposed to the 

 muscles which have a tendency to push the abdominal organs into the thorax ? Above all, how can the inspiratory 

 and expiratory acts (seeing the latter put the viscera in motion) " be balanced so nicely that the most dehcate 

 vocal vibrations can be produced " ? 



The confusion and inconsistencies referred to above are the result of an erroneous conception of muscular 

 action and muscular arrangements, and of the part which elasticity is supposed to play in all muscular effort. 



1 " A Ti'xt-lteok of Huiiiiiri Pliysiology," by Austin Flint, junior, M.D., Professor of Physiology and Pliysiological Anatoniv RhUpvup 

 Hospital and Jlidical College, Xkw York ; pp. 554, 555. ' ■'' "^'"-'^"'- 



