Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/38

28 ORNITHOLOGY he also examined ; and he practically, though not literally, 1 asserted the truth, when he said that the general struc ture, but especially the muscular appendages, of the lower larynx was " similarly formed in all other birds of this family " described in Audubon s work. Macgillivray did not, however, assign to this essential difference any systematic value. Indeed he was so much prepossessed in favour of a classification based on the structure of the digestive organs that he could not bring himself to con sider vocal muscles to be of much taxonomic use, and it was reserved to JOHANXES MULLER to point out that the ller - contrary was the fact. This the great German compara tive anatomist did in two communications to the Academy of Sciences of Berlin, one on the 26th June 1845 and the other on the 14th May 1846, which, having been first briefly published in the Academy s Monats?>ericht, were afterwards printed in full, and illustrated by numerous figures, in its Abhand1un<jen y though in this latter and complete form they did not appear in public until 1 847. This very remarkable treatise forms the groundwork of almost all later or recent researches in the comparative anatomy and consequent arrangement of the Passeres, and, though it is certainly not free from imperfections, many of them, it must be said, arise from want of material, not withstanding that its author had command of a much more abundant supply than was at the disposal of Nitzsch. Carrying on the work from the anatomical point at which he had left it, correcting his errors, and utilizing to the fullest extent the observations of Keyserling and Blasius, to which reference has already been made, Miiller, though hampered by mistaken notions of which he seems to have been unable to rid himself, propounded a scheme for the classification of this group, the general truth of which has been admitted by all his successors, based, as the title of his treatise expressed, on the hitherto unknown different types of the vocal organs in the Passerines. He freely recognized the prior discoveries of, as he thought, Audubon, though really, as has since been ascertained, of Macgillivray ; but Miiller was able to perceive their system atic value, which Macgillivray did not, and taught others to know it. At the same time Miiller shewed himself, his power of discrimination notwithstanding, to fall behind Nitzsch in one very crucial point, for he refused to the latter s Picarix the rank that had been claimed for them, and imagined that the groups associated under that name formed but a third " Tribe " Picarii of a great Order Insessores, the others being (1) the Oscines or Polymyodi the Singing Birds by emphasis, whose inferior larynx was endowed with the full number of five pairs of song- muscles, and (2) the Tracheophones, composed of some South-American Families. Looking on Miiller s labours as we now can, we see that such errors as he committed are chiefly due to his want of special knowledge of Ornithology, combined with the absence in several instances of sufficient materials for investigation. Nothing whatever is to be said against the composition of his first and second " Tribes" ; but the third is an assemblage still more heterogeneous than that which Nitzsch brought together under a name so like that of Miiller for the fact must never be allowed to go out of sight that the extent of the Picarii of the latter is not at all that of the Picarix of the former. 2 For instance, Miiller places in his 1 Not literally, because a few other forms such as the genera Polio- ptikin.n< Plilogonys, now known to have no relation to the Tyrannidir, were included, though these forms, it would seem, had never been dis sected by him. On the other hand he declares that the American Redstart, Muscicapa, or, as it now stands, Ketnphaga ruticilla, when young, has its vocal organs like the rest an extraordinary statement which is worthy the attention of the many able American ornithologists. 2 It is not needless to point out this fine distinction, for more than one modern author would seem to have overlooked it. third " Tribe " the group which he called Ampelufa, mean ing thereby the peculiar forms of South America that are now considered to be more properly named Cotingidse, and herein he was clearly right, while Nitzsch, who (misled by their supposed affinity to the genus Am pelts peculiar to the Northern Hemisphere, and a purely Passerine form) had kept them among his Passerinx, was as clearly wrong. But again Miiller made his third "Tribe" Picarii also to contain the Tyrannidx, of which mention has just been made, though it is so obvious as now to be generally admitted that they have no very intimate relationship to the other Families with which they are there associated. There is no need here to criticize more minutely his pro jected arrangement, and it must be said that, notwithstand ing his researches, he seems to have had some misgivings that, after all, the separation of the Insessores into those " Tribes " might not be justifiable. At any rate he wavered in his estimate of their taxonomic value, for he gave an alternative proposal, arranging all the genera in a single series, a proceeding in those days thought not only defens ible and possible, but desirable or even requisite, though now utterly abandoned. Just as Nitzsch had laboured xinder the disadvantage of never having any example of the abnormal Passeres of the New World to dissect, and therefore was wholly ignorant of their abnormality, so Miiller never succeeded in getting hold of an example of the genus Pitta for the same purpose, and yet, acting on the clew furnished by Keyserling and Blasius, he did not hesitate to predict that it would be found to fill one of the gaps he had to leave, and this to some extent it has been since proved to do. The result of all this is that the Oscines or true Pnssors are found to be a group in which the vocal organs not only attain the greatest perfection, but are nearly if not quite as uniform in their structure as is the sternal apparatus ; while at the same time each set of characters is wholly unlike that which exists in any other group of Birds. In nearly all Birds the inferior larynx, or syrinx, which i., as proved long ago by the experiments of Cuvier, the scat of their vocal powers, is at the bottom of the trachea or windpipe, and is formed by the more or less firm union of several of the bony rings of which that tube is composed. In the Ratitie, the genus Jlhca excepted, and in one group of Carinatse, the American Vultures Cathartidse, but therein it is believed only, there is no special modification of the trachea into a syrinx ; 3 but usually, at a little distance from the lungs, the trachea is somewhat enlarged, and here is found a thicker and stouter bony ring, which is bisected axially by a septum or partition extending from behind forwards, and thus dividing the pipe, 4 each half of which swells out below the ring and then rapidly contracts to enter the lung on its own side. The halves of the pipe thus formed are the bronchi, tubes whose inner side is flattened and composed of the mcmlrana fi/)i>piiiii- formis, on the change of form and length of which some of the varieties of intonation depend, while the outer and curved side is supported by bony half-hooj s, connected by membrane just as arc the entire hoops of the upper part of the trachen. The whole of this apparatus is extremely flexible, and is controlled by muscles. the real vocal muscles of which mention has previously been so frequently made. These vary in number in different groups of Birds, and reach their maximum in the Oscim:*, which have always five pairs, or even more according to some authorities. 5 But sup posing five to be the number of pairs, as it is generally allowed to be in this group of them, two pairs have a common origin about the middle of the trachea, and, descending on its outside, divide at a short distance above the lower end of the tube ; one of them, the tensor posterior tom/ns, being directed downward and backward, is inserted at the extreme posterior end of the first half-ring of the; bronchus, while its counterpart, the tensor anterior loiiyits, passing from the place of separation downward and forward, is inserted below the extreme point of the lust ring of the trachea. "Vithin the angle formed by the divergence of each of these pairs of muscles, a third slender muscle the stcrno-lrac/tealis is given oil 3 See BIRDS, vol. iii. p. 726 ; but rf. Forbes, Prac. ZooL Society, 1881, pp. 778, 788. 4 In a few forms belonging to the Xpheniscidx. and ProcettariidK, this septum is prolonged upwards, to what purpose is of course unknown. On the other hand, the Parrots have no septum (see BIKDS, ut supra). 5 See BIRDS, vol. iii. p. 726.