THE MAMMALIA— MAN AND BEASTS. 



93 



The Mammalia differ considerably from Birds, in respect to their organs of voice. 

 In the latter, the several varieties of sound are produced in a more simple manner ; 

 and, from the organs of voice in the Birds approaching very near, in tlie principles of 

 their structure, to several weil-known musical instruments, they are, at the same 

 time, more fully understood. But the cries of the Mammalia are most commonly of 

 a very complicated and discordant nature, so that we may attempt in vain to imitate 

 them by any mechanical means. 



In ordinary language, we understand by the term voice, those sounds which ani- 

 mals produce in expelling the air from their lungs, through the opening of the glottis. 

 From the above definition, it follows, that animals with lungs, being the first three 

 Classes of Vertebrated Animals, the Mammalia, Birds, and Reptiles, can alone enjoy 

 this power. 



The voice, being formed of vibrations communicated to the air, consists, like all 

 other sounds, of three orders of properties, perfectly distinct from each other : (1.) 

 The tone, or the different degrees of depth and acuteness, which depend on the slow- 

 ness or rapidity of the vibrations ; (2.) The intensiti/, or different degrees of loud- 

 ness, regulated by the extent of thj vibrations; and, (3.) The quality, which de- 

 pends upon a variety of circumstances hitherto undetermined, relative either to the 

 internal structure, the substance, or the figure of the sonorous body, Man alone 

 being capable of speech, becomes susceptible of a fourth order df modifications, which 

 we represent by tho letters of the alphabet. These may be further divided into two 

 sub-orders — the one, relative to the principal sounds, which we represent by vowels ; 

 and the other dependant upon their mode of articulation, and distinguished by the 

 consonants. Those circumstances which give rise to the several qualities of tone, 

 and the articulate words of Man, are still involved in great obscurity, although the 

 investigations of De Kempelin in 1791, and the more recent experiments of Messrs 

 Willis and Wheatstone, demonstrate that it is not impossible to imitate the sounds of 

 the human voice by certain mechanical contrivances. 



In respect, however, to the tone and intensity of sounds, the theory has long been 

 well understood. We know that the rapidity of the vibrations of cords is inversely 

 proportional to the length of the latter, and durectly proportional to the degree 

 of their tension. It is also ascertained, that a cord producing a tone will give 

 at the same time others corresponding to the ahquot parts of its length, such 

 as the half, the third, or the quarter ; and the sounds thus formed are termed 

 harmonic tones or chords. The vibrations of the entire cord coincide with the 

 smaller but more rapid vibrations of the aliquot parts, and the sounds thence resulting 

 are found to be harmonious, or agreeable to the ear. We further know that wind 

 instruments of music can produce sounds corresponding to their total length, at the 

 same time that they emit others relative to the lengths of their aliquot parts ; and 

 that it merely requires some appai-ently very slight cause, whether with cords or 

 wind instruments of music, to occasion one of these partial or harmonic tones to pre- 

 vail over the whole or fundamental tone. It has also been remarked, in respect to 

 the tubes of wind instruments, that their form, in most cases, does not ali^ct the 

 tone. If the extremity opposite to the embouchure be closed, they produce a sound 

 corresponding to a tube of twice their length, but when it is only partially closed, as 

 in the chimney or funnel-pipes of the organ, the tone is always more gravv.' than if it 

 bad been open, but less so than when entirely closed. Wind instruments of music can 

 emit no sound by simply blowing into the tube. There must be at the entrance of 

 the tube some sonorous body, that is to say, a thin plrne capable of vibrating, or at 

 least of breaking the current of air against its edge. This condition is absolutely 

 essential to the production of sound, properly so called. 



The organ of voice, being found only in animals possessing lungs, always consists 

 of the canal formed by the bronchial tubes, the trachea, and the mouth ; in other 

 words, of an irregular tube to which the lungs act as bellows. The planes capable 

 of breaking the air and producing a true sound may, however, be placed in different 

 positions relative to the length of the tube. The entire portion comprised between 

 the vesicles of the lungs and these vibrating planes, which have received the name of 

 glottis, may be considered as nothing more than the nozzle of the bellows. That 

 portion of the tube placed beyond these planes, being the larynx, must alone be 

 regarded as the sonorous instrument, whose length and other circumstances serve to 

 influence and modify the voice. 



B.'any Birds are found to possess, in the interior of their bronchial tubes, small 

 planes, being a kind of rudimentary glottis ; but all of them have a complete one at 

 the point where their bronchial tubes unite in forming the trachea. On this account 

 we should thence regard the trachea itself in all Birds as a true musical instrument. 

 In the Mammalia and Reptiles, on the contrary, no glottis is found except at the 

 upper extremity of the trachea, where it enters the mouth. We must, therefore, 

 consider the mouth in these animals as the real instrument of music, and the trachea 

 with them is merely a wind-pipe or porte-vent. 



It thus appears that the voice of animals is formed by the air which is discharged 

 from the luno^s by the muscles of expiration ; that it traverses the bronchial tubes, 

 and sometimes also the trachea; and arrives at a contracted portion, edged with two 

 thin and flexible planes, called the glottis, where the sound is really produced. It then 

 traverses a second tube, consisting either of the trachea and mouth or of the mouth 

 solely, where it receives the last modifications, from the length, the form, and the 

 differences in the complication of these cavities. Finally, it passes between the lips, 

 which may be more or less opened or differently formed. 



The possible intensity of the voice depends upon the proportional volume of the 

 lungs and aerial cavities, and hence results the extraordinary volume of voice possessed 

 by most Birds. The facihty of modulating the voice during singing depends upon 

 the facility of motion possessed by the muscles which contract the lungs. That por- 

 tion of the trachea or the bronchial tubes- situate within the glottis, cannot influence 

 the quality of the sound, excepting, perhaps, that the proportion of its diameter, in 

 respect to the glottis, may influence the possible velocity of the air in its passage. 

 The gluttis itself affects the sound like the embouchure of a wind instrument of mu- 

 sic, while that portion of the canal situate externally to it acts like the tube of the 

 instrument, inasmuch as its several lengths determine the respective fundamental tones 

 which the animal can assmne; while the glottis, by its tension and the shape of its 

 24 



orifice, occasions the several harmonic tones of the fundamental note belonging to each 

 particular length. The external opening may lastly be compared to the remote ex- 

 tremity of the organ-tube, which may be more or less closed. Upon the facility with 

 which an animal can vary these three conditions depends the extent and flexibility 

 of its voice. 



Those modifications which we represent by the letters of the alphabet, are formed 

 in the mouth, and depend upon the greater or less power of motion possessed by the 

 tongue, and especially by the lips, to which circumstances Man owes the superior 

 power of speech. Some animals which seem to possess considerable flexibility in their 

 organs of voice have certain additional parts, nullifying the advantageous form of the 

 others, such as cavities, in which the air is obliged to circulate after leaving the 

 glottis. 



In respect to the Mammalia generally, we are far from having a complete know- 

 ledge of their manner of producing those disagreeable and complicated noises which 

 our musical instruments fail to imitate. A few general facts have, however, been as- 

 certained. Thus, the interval of the fibrous, and more or less sharp, cords of the 

 larynx, placed on the upper extremity of the trachea, and called the vocal cords, is 

 the place where the sound is formed ; while the size, freedom, and tension of these 

 cords influence the sound at its very origin. As the entire trachea serves merely as 

 a wind-pipe, it varies little in its form. The rings are scarcely ever complete, but 

 leave behind them a simple, membraneous band. 



The sound produced by the vocal cords, or inferior ligaments of the glottis, may be 

 modified, 



i . By the form and dimensions of the passage opened for it as it traverses the 

 remaining parts of the larynx ; 



2. By the resounding or dispersion of the sound in the cavities contiguous to the 

 larynx, such as the ventricles of the glottis, the furrows and pouches which some- 

 times communicate with it, or the pouches which occasionally open in front of the 

 larynx ; 



And, lastly, By the form and dimensions of the double passage furnished by the 

 mouth and nostrils, or by the different positions of the tongue and lips. 



It would be inexpedient to pursue this subject in detail at present, and our further 

 observations upon those modifications which influence the voice will be found under 

 the specific descriptions. 



GENERAL REVIEW OF THE MAMMALIA CONTINUED. 



Anomalous adaptations for motion and prehension. — Special organizations for 

 digging, flying, and swimming. 



Although some Mammalia possess the power of plunging in the water, of elevating 

 themselves in the air, or of burrowing under ground, these seem rather to be anoma- 

 lous states of existence. The normal or proper state of their organization fits them 

 more especially for terrestrial animals. 



Among those destined to reside upon the earth, Man alone has his fore extremities 

 adapted solely for prehension, and his hinder limbs for maintaining the body in an 

 erect posture. We shall merely remark at present, that he owes this vertical posi- 

 tion chiefly to the size of the soles of his feet ; the largeness of the muscles belonging 

 to the legs and thighs; the breadth of the pelvis; the position of the head upon the 

 neck ; and the shortness of the arms when compared with the length of the legs. It 

 follows from these arrangements, that his forward movement consists simply in the 

 succ:;ssive position of the lower extremities one before the other and in parallel lines, 

 while running differs but little from walking, except in the greater rapidity of the 

 action. 



It is different in the true Quadrupeds, where the extremities are very nearly of equal 

 length. In these we have a variety of modes of progression ; such as the walk or 

 pace, where the two diagonal feet, either the right fore and the left hind foot, or the 

 left fore and the right hind foot, act successively, but in such a way that the advance 

 of the fore foot is almost instantaneously followed by the advance of the hind foot on 

 the opposite side, so that the four feet are raised and set down one after another. In 

 a more rapid pace, being the trot, the two feet diagonally opposite rise and are set 

 down at the same instant. The canter or common gallop, the full gallop, and the 

 amble, have been already explained (see page 26), els well as the auhin, or Spanish 

 amble, and the pas releve of French authors (see page 63). 



The greater number of Quadrupeds, when they wish to advance slowly, go at a 

 simple walk. The trot is the proper motion of certain species, such as the Plorpe, 

 the Fox, some races of Dogs, the Bear, and of the Elephant when hurried. The 

 amble is the natural pace of certain races of the Horse and Dog, and invariably so 

 with the Hysna, which circumstance gives a singular and striking appearance to the 

 gait of that animal. The canter, and especially the full gallop, are used by most land 

 Mammalia when hotly pursued, or when they are in pursuit of any prey. 



Those Mammalia having the fore extremities much longer than the hinder, are pre- 

 vented from walking upright like Man, or on the four feet like the Quadrupeds. The 

 position of their body is therefore oblique, and their speed on a flat surface being very 

 limited, they are more disposed to climb trees than tu use any other kind of exercise. 

 There arc other Mammalia, such as the Jerboas, the Gerbils, the Kangaroo, and the 

 Kangaroo- Rat, where the hinder are very considerably longer than the fore legs, which 

 seem by their excessive shortness to depart as much in defect from the ordinary size 

 as the others do in excess. These animals walk with great diflSculty. The Kanga- 

 roos in particular make use of their tail, which is of considerable strength and size, 

 either to counterpoise the weight of the fore extremities, or to assist in raisin^ the 

 body, while the fore paws touch the ground. When they run, or rather jump, for 

 such is their real motion, the hinder feet alone act, and propel the body to a consider- 

 able distance in advance. The tail, however, follows to their assistance, and the 

 moment the feet touch the ground, it extends and forms with the two metatarsi a 

 kind of tripod, which maintains their upright position, and enables the animal to exe- 

 cute a new leap. As another instance of this kind of movement, wc may adduce the 

 Jerboas, animals abvut the size of a Rat, with their hinder feet much longer in pro- 



