58 DESCRIPTIONS OF PREPARATIONS. 



Thymus. Afannassiew, A. M. A. xiv. 1877, p. 346. 



Kidney. Heidenhain, A. M. A. x. 1874, p. 20. Hufner, Zur Vergleich. Anat. 

 u. Physiol. der Harnkanalchen, Dissertation, Leipzig, 1866. 



Oviduct. Blasius, Z. W. Z. xvii. 1867. Albumen glands (also of Amphibia), 

 Loos, Z. W. Z. xxxv. 1 88 1. 



On the mechanism of flight. See Garrod, P. Z. S. 1875, and in Anat. of 

 Passerine Birds, with 4 Plates, P. Z. S. 1876. Strasser, J. Z. xix. 1885. Marey, 

 Animal Mechanism (Internat. series), xi. 1874. Pettigrew (same series), vii. 1874; 

 and Trans. Roy. Soc. Edinburgh, xxvi. 1872. 



On muscles of wings. Schopss, Meckel's Archiv f. Anat. u. Physiol. 1829. 

 Sundevall, Brit. Ass. Reports, 1855. Rolleston, Homology of Muscles of Shoulder 

 Joint, Tr. L. S. xxxi. 1870 (cf. a paper by Fiirbringer, M. J. i. 1876). Garrod, 

 P. Z. S. 1873 and 1874. Fiirbringer, M. J. xi. 1885. 



On muscles of hinder extremities. Garrod, P. Z. S. 1873 and 1874. Gadow, 

 Zur Vergleich. Anat. der Muskulatur des Beckens, &c. der Ratiten, Jena, 1880. 



Value of innervation in determining homology of a muscle. Fiirbringer, J. Z. vii. 

 1873, p. 240. Cunningham, Journal of Anat. and Physiol. xvi. 1882. 



II. 



THE SKELETON OF THE COMMON PIGEON (Colmnba livia). 



A Bird's skeleton has characters both peculiar and well-marked. The 

 bones undergo extensive anchylosis especially in the skull, pelvic region, 

 hand and foot The bone-substance is dense, and is stated to contain 

 a large proportion of lime phosphate. The cancellated tissue with the 

 marrow is frequently absorbed and its place taken by air derived in the 

 skull from the nasal passages and tympanic cavities : in the rest of the 

 skeleton from extensions of the air-sacs connected with the lungs. All the 

 bones in the Pigeon contain air, i. e. are pneumatic, save the caudal vertebrae, 

 the fore-arm and hand and hind-limb. 



The skull presents the following general features : It has, like the 

 Reptilian skull, a single condyle. The cranial surface is smooth, polished, 

 and its sutures obliterated. The orbital cavities are large and separated 

 one from another by a thin vertical inter-orbital septum, formed chiefly 

 by the mesethmoid. The orbit is bounded in front by the lacrymal bone 

 and the homologue of the lateral mass of the ethmoid in man. The beak 

 consists mainly of the praemaxillae, which are continued backwards 

 below the orbit by a slender bony rod. The anterior part of this rod is the 

 maxilla, the posterior which articulates with the quadrate, a jugo-quadrato- 

 jugal bone. A moveable quadrate articulates with the skull on the one hand, 

 and the lower jaw on the other. The two rami of the mandible are 

 anchylosed at the symphysis. A ring of bony plates developed in the 

 sclerotic of the eye is seen suspended in the left orbit. A similar ring 

 is found in many Lacertilia, the Chelonia, and extinct Ichthyosauria. 



The vertebral column is divisible into a cervical, dorsal, so called 



