596 OSTEOLOGY OF LARID^. 



The above table differs from tbose giveu by Owen, ToclcVs Cyclop. Anat. and Phys., 

 Art. Aves, and by Eyton, Osteol. Avium. Prof. Owen's tiguies are : " Catarractes," V.i — 

 9—13—8; "Gh/«," 18—8—11—8; " Tm(," 14— 8— 10— 8. Mr. Eyton gives: Larua ridi- 

 iundus, 14 — 7 — 12 — 7; Sterna arciica, 13 — G — 12 — 6; Bhyncliops vujra, 13 — 6 — 12 — 8. It 

 is' to be expected that discrepant statements should occur in the enumeration of the 

 sacral vertebrai, as the coniijosition of that most complex of all bones is difficult to 

 interpret. In the other instances we may presume that there is actually a variation 

 ■with the species in number of vertebrae of the several regions. I give the numbers as 

 determined by myself in the specimens of the three siiecies above mentioned, adding 

 the formuliB of Owen and Eyton for comparison. 



The xieculiarities of the several regions, and of the different vertebra*, composing 

 them, may be briefly noticed : 



Cekyical vertebk.e. — The atJas is little more than a simple ring, its foramen slightly 

 flattened interiorly. Its "body " is merely a slight projection on the inferior edge of its 

 circumfereuce ; bearing, cephalad, a perfectly circular facet for articulation with the 

 occipital condyle; and caudad, and upon its superior margiu, a deep longitudinal 

 channel, so deep as almost to amount to a canal for the reception and retention of the 

 axial odontoid process. Superiorly on each side are indications of transverse pro- 

 cesses; iuferiorly there is the rudiment of a " ventral spine." 



Axis. — This is of a somewhat peculiar shape. The spiuous and transverse processes, 

 both of which are quite well developed, seem to lie considerably posterior to the 

 body of the vertebra, in cousequeuce of an obliquity backward of the neural arch 

 from the centrum. The ventral spine is well developed, thin, with an anteriorly con- 

 vex, j)osteriorly concave margin; oblique in direction, projecting backward as well as 

 downward. The body of the vertebra proper consists of little more than a base for 

 the support of the odontoid process, which latter is acute, well developed, semicylin- 

 drical, its surface toward the spinal canal being flattened. The transverse articulating 

 facets are small, subcircular, slightlj' concave, situated beneath the processes, at their 

 bases. The other articulation is elongated, compressed, vertically concave, hori- 

 zontally convex. The motion between the atlas and the third vertebra is very free in 

 a vertical direction, less so in a horizontal, while rotation is greatly restricted. 



The third and fourth vertebra somewhat resemble the axis in having a broad, thin, 

 longitudinal lamina of bone extending between the anterior and posterior articular 

 lirocesses. They are also very short and broad. The other vertebra} all differ some- 

 what, but the difference is so gradual that they may most conveniently be described 

 collectively. The lowest or dorsad vertebrre are the largest and broadest, but com- 

 paratively the shortest. Their posterior articular processes are short and slightly 

 divaricating; as we proceed nj) the neck they become longer, more attenuated, and 

 more widely diverging. This attenuation is greatest on about the fifth vertebra. 

 The transverse processes are very wide below, and extend directly outward from the 

 median line. Further up the neck they are less promineut, and have also an anterior 

 obliquity. This process on the last vertebra does not form a canal for the passage of 

 the artery; the canal commences on the twelfth, as a simple foramen, becoming nar- 

 rower in diameter, but at the same time more and more lengthened aiid canal-like, up 

 to the atlas. 



Superior spinous processes, or the "neural spines," are well developed on the first 

 five vertebra?, but they diminish in size from the third to the sixth, when they become 

 quite obsolete, and do not reappear. Inferior or ventral sjiiuous processes are found 

 very well develoj)ed on the first four vertebra}, being largest on the atlas; they then 

 entirely disappear, and are not found again until about the eleventh vertebra, where 

 they are slightly elevated, longitudinal, vertical lamelLo}. Styloid processes are found 

 throughout the whole length of this portion of the spine, except the atlas and axis, 

 and, usually, the last vertebra. They commence on the third vertebra, elongate on 

 each successively to the sixth or seventh, where they are longest and thinnest, meas- 

 uring two-thirds the length of the body of the vertebra. They then regularly grow 

 shorter and more obtuse till they are hardly perceptible on the thirteenth and quite 

 obsolete on the fourteenth or last cervical. 



Air is admitted into the vertebne by numerous foramina on the sides of the bodies, 

 about the roots of the transverse processes and in the canal for the artery. 



There is the ordinary difference in the calibre of the spinal canal in the centre and 

 at the extremities of each vertebra. The planes of the articular surface are, as usual, 

 so disposed as to produce, in the most natural position of the head and neck, the ordi- 

 nary sigmoid flexure. When the neck is extended there is on the dorsal surface a 

 large diamond-shaped space between each vertebra and the next covered in only by 

 ligamentous tissue. 



l>oi:sAL YEKTEBi^E. — If WO regard the presence of a rib as characteristic of the ver- 

 tebra; of this region of the spiue, we shall have eight as the total number of dorsal 

 vertebra}. But the two last of these are perfectly consolidated with and continuous 

 wilh Uie first sacral; and their transverse and spiuous processes also have a lateral 

 ai;d superior anchylosis with the iliac bones. At the same time there is a perfect artic- 



