Page:EB1911 - Volume 03.djvu/989

 failure. Its author, with a considerable mathematical and mechanical bias, reckoned entirely with the quantity, not with the quality of his units, and relied almost implicitly upon his formulae. It is, however, fair to state that his system was not built entirely upon these muscular variations, but rather upon a more laborious combination of anatomical characters, which were so selected that they presumably could not stand in direct correlation with each other, notably the oil-gland, caeca, carotids, nasal bones and above all, the muscles of the thigh. He was, indeed, the first to show clearly the relationship of the heron-like birds with the Steganopodes; of stork-like birds with the American vultures; the great difference between the latter and the other birds of prey; the connexion of the gulls and auks with the plovers, and that of the sand-grouse with the pigeons—discoveries expressed in the new terms of the orders Ciconiiformes and Charadriiformes. These are instances, now well understood, that almost every organic system, even when studied by itself, may yield valuable indications as to the natural affinities of the various groups of birds. That Garrod has so very much advanced the classification of birds is ultimately due to his comprehensive anatomical knowledge and general insight.

To return to these thigh muscles. The most primitive combination, ambiens and A B X Y, is the most common; next follows that of A X Y, meaning the reduction of B, i.e. the iliac portion of the caud-ilio-femoralis; A B X and B X Y are less common; A X and X Y are rare and occur only in smaller groups, as in subfamilies or genera; B X occurs only in Podiceps. But the greatest reduction, with only A remaining, is characteristic of such a heterogeneous assembly as Accipitres, Cypselidae. Trochilidae, Striges and Fregata. This fact alone is sufficient proof that these conditions, or rather reductions, have been acquired independently of the various groups. A B Y, A Y, A B, X Y and B do not occur at all, some of them for obvious reasons. Occasionally there is an instructive progressive evolution expressed in these formula; for instance Phaethon, in various other respects the lowest of the Steganopodes, has A X Y, Sula and Phalacrocorax have A X, Fregata, the most specialized of these birds, has arrived at the reduced formula A. Further, the combinations B X Y and A X Y cannot be derived from each other, but both directly from A B X Y in two different directions. Keeping this in mind, we may fairly conclude that the flamingo with B X Y points to an ancestral condition A B X Y, which is still represented by Platalea and Ibis, whilst the other storks proper have taken a different line, leading to A X Y.

.—Well nigh complete lists of the enormous myological literature are contained in Fürbringer’s Untersuchungen zur Morphologie und Systematik der Vögel, and in Gadow’s vol. Vögel of Bronn’s Klassen und Ordnungen des Tierreichs. Only a few papers and works can be mentioned here, with the remark that few authors have paid attention to the all-important innervation of the muscles. A. Carlsson, Beiträge zur Kenntniss der Anatomie der Schwimmvögel; K. Svensk, ''Vet. Ak. Handlinger. J. G. No. 3 (1884); A. Alix, Essai sur l’appareil locomoteur des oiseaux (Paris, 1874); H. Gadow, Zur vergl. Anat. der Muskulatur des Beckens und der hinteren Gliedmasse der Ratiten, 4° (Jena, 1880); A. H. Garrod, “On Certain Muscles of the Thigh of Birds and on their value in Classification,” P.Z.S.'', 1873, pp. 624-644; 1874, pp. 111-123. Other papers by Garrod, 1875, pp. 339-348 (deep planter tendons); 1876, pp. 506-519 (wing-muscles of Passeres), &c.; J. G. de Man, Vergelijkende myologische en neurologische Studien over Amphibien en Vogels (Leiden, 1873), (Corvidae); A. Milne-Edwards, Recherches anatomiques et paléontologiques pour servir à l’histoire des oiseaux fossiles de la France (Paris, 1867–1868), tom. i. pls. ix.-x. (Aquila and Gallus); R. Owen, article “Aves,” Todds’ ''Cyclopaed. of Anat. and Phys. i. (London, 1835); “On the Anatomy of the Southern Apteryx,” Trans. Zool. Soc., iii., 1849; A. Quennerstedt, “Studier i foglarnas anatomi,” Lunds Univers. Aarsk., ix., 1872 (hind-limb of swimming birds); G. Rolleston, “On the Homologies of Certain Muscles connected with the Shoulder-joint,” Trans. Linn. Soc., xxvi., 1868; R. W. Shufeldt, The Myology of the Raven (London, 1891); M. Watson, “Report on the Anatomy of the Spheniscidae,” Challenger Reports'', 1883.

3. Nervous System.

Brain.—The more characteristic features of the bird’s brain show clearly a further development of the reptilian type, not always terminal features in a direct line, but rather side-departures, sometimes even a secondary sinking to a lower level, and in almost every case in a direction away from those fundamentally reptilian lines which have led to the characters typical of, and peculiar to, the mammals.