COMPARATIVE ANATOMY. 



animal kingdom, possess a true voice. 

 Several genera and species even of these 

 are either entirely dumb, as the anteater, 

 the manis, the cetacea, the genus testudo, 

 several lizards, and serpents; or they 

 lose their voice in certain parts of the 

 earth, as the dog in some countries of 

 America, and quails and frogs in several 

 parts of Siberia. 



Most mammalia have the following cir- 

 cumstances in common : their rim a glot- 

 tidisis provided with an epiglottis, which 

 in most instances has a peculiar muscle, 

 arising from the os hyoides, and not 

 found in the human subject : the mar- 

 gins of this rima are formed by the double 

 ligamenta glottidis (ligamenta thyreoary- 

 txnoidea) ; between which the ventri- 

 culi laryngis are formed. The epiglottis 

 does not exist in most of the but kind : 

 and in some mouse-like animals, as the 

 rell-mouse (glis csculentus,) it is hardly 

 discernible. The superior ligamenta 

 glottidis, as well as the ventriculi laryngis, 

 are w anting in some bisulca, as the ox 

 and sheep. 



Some species of mammalia have a pe- 

 culiar and characteristic voice ; or at 

 least certain tones, which are formed bv 

 additional organs. Of this kind are cer- 

 tain tense membranes in some animals; 

 and in others peculiar cavities, opening 

 into the larynx, and sometimes appear- 

 ing us continuations of the ventriculi la- 

 ryngis. 



The neighing of the horse, for ex- 

 ample, is effected by a delicate and 

 nearly falciform membrane, which is at- 

 tached by its middle to the thyroid car- 

 lilage, and has its extremities running 

 along the external margins of the rima 

 glottidis. 



The peculiar sound uttered by the ass 

 is produced by means of a similar mem- 

 brane, under which there is an excava- 

 tion in the thyroid cartilage. There are 

 moreover two large membranous sacs 

 openng into the larynx. 



The mule does not neigh like the mare 

 by which it was conceived, but brays like 

 the ass which begot it. It possesses 

 exactly the same larynx as the latter, 

 without any of the peculiar vocal organs 

 of the mother; a fact which, like many 

 others, cannot be at all reconciled with 

 the supposed pre-existence of previous- 

 ly formed germs in the ovarium of the 

 mother. 



Several apes and baboons, as also the 

 rein-deer, have on the front of the neck 

 large single or double laryngeal sacs, of 

 various forms and divisions, communicat- 

 ing with the larynx by one or two open- 



ings between the os hyoides and thyroid 

 cartilage. 



Some of the cercopitheci, as the C. Se- 

 niculos, and beelzebub, have the middle 

 and anterior part of the os hyoides 

 formed into a spherical bony cavity, by 

 which the animals are enabled to pro- 

 duce those terrific and penetrating tones, 

 which can be heard at vast distances, and 

 have gained them the name of the howl- 

 ing apes. 



The most striking peculiarity in the 

 vocal organs of birds, and which be- 

 longs to all birds, with very few excep- 

 tions, consists in their possessing what 

 is commonly called a double larynx, 

 but which might be more properly de- 

 scribed as a larynx divided into two 

 parts, placed at the upper and lower 

 ends of the trachea. They have also two 

 rimae glottidis. 



The superior, or proper rima glottidis, 

 is placed at the upper end of the tra- 

 chea ; but is not furnished with an epi- 

 glottis. The apparent want of this organ 

 is compensated in several cases by the 

 conical papillae placed at both sides of the 

 rima. 



The apparatus which is chiefly con- 

 cerned in forming the voice of birds is 

 found in the inferior or bronchial larynx. 

 This contains a second rima glottidis, 

 formed by tense membranes, which may 

 be compared in several cases, particular- 

 ly among the aquatic birds, to the reed at 

 the mouth of musical instruments. It is 

 furnished externally with certain pairs of 

 muscles, varying in number in the diffe- 

 rent orders and genera; and with a kind 

 of thyroid gland. The course and pro - 

 portionate length of the trachea, and 

 particularly the structure of the inferior 

 larynx, vary very considerably in the 

 different species, and even in the two 

 sexes, especially among the aquatic birds. 

 Thus, for example, the tame or dumb 

 swan (anus olor) has a straight trachea ; 

 whilst in the male of the wild, or whist- 

 ling swan (cygnus), this tube makes a 

 large convolution, which is contained in 

 the hollow of the sternum. In the spoon- 

 bill (Platalea leucorodia), as also in the 

 Fiiasianus motmot, and others, similar 

 windings of the trachea are found, not en- 

 closed in the sternum. Thfe males of 

 the two genera, anas and mergus, have at 

 their inferior or bronchial larvnx a bony 

 cavity, which contributes to strengthen 

 their voice. 



A very little comparison of the me- 

 chanism of wind musical instruments 

 with the organs of the voice in birds, will 

 shew how ncarlv thev arc allied to each 



