146 



GENERAL OliXlTHOLOGY. 



anchylosis of their oodies and processes, but also, in many cases, by ossifications of the 

 tendons of muscles of the back, and coost-ifications of these with the vertebrae, like a set of 

 splints, till the consolidation of the thoracicis only surpassed by that of the pelvic region of the 

 spine. Dorsal vertebrae also usually differ a good deal from most cervicals in having shorter 

 bodies, laterally compressed, producing a ridge which runs along their middle line below ; in 

 lacking a vertebrarterial canal ; in having on each side two articular facets, — one on the body 

 and the other on the transverse process, for the head and shoulder of a rib. They are further 

 distinguished, usually, by having large spinous processes, in the form of high, long, thin, 

 squarish plates, often or usually anchylosed together. Their transverse processes are alst) 

 very prominent laterally, thin and horizontal, and often anchylosed. More or fewer dorsals 

 may bear large hypapophyses ; which, as in the loon, may bifurcate at their ends into two 

 flaring plates. Such processes continue a similar series from the neck, and are in relation to 

 the advantageous action of the muscles (rectus colli anticus and longus colli) by which the 

 neck is made to straighten out from the lower curve of its sigmoid flexure. 



The " Sacrum " of a Bird (figs. 57, and 60) is commonly considered to be that large 

 solid mass of num('riiu.s anchylosed vertebras in the region of the pelvis, covered in by, and 

 fused more or less completely with, the principal bones of the 

 pelvis, or haunch-bones (ilio). But in this consolidation of an 

 extremely variable number (averaging perhaps twelve, but run- 

 ning up to at least twenty, eleven to thirteen being usual) 

 of bones are included vertebrae which in other animals belong 

 to several different sets — dorsal, lumbar, sacral proper, and 

 coccygeal or caudal. We have just seen that one or two, even 

 three, vertebrae, which are dorsal according to the definition 

 agreed upon, may enter into the composition of the " sacrum," 

 being firmly anchylosed therewith, and their long ribs issuing 

 (tut from underneath the ilia, as shown in fig. 5fi, sr. Next 

 comes one bone, or a series of several (two to five or morel 

 bones, anchylosed together by their bodies and Sjiiuous proc- 

 esses, and also anchylosed with the ilia by means of stout lateral 

 bars of bone sent transversely outward on either side from their 

 respective centra to abut against the ilia. These cross-bars 

 correspond in general form and position with the transverse 

 process of the last true rib-bearing dorsal, — that process against 

 which the shoulder of any developed rib abuts ; they are variously 

 considered to be, to represent, or to include rudimentary ribs; 

 and such difference of view may be warranted by the state of the 

 parts in different birds. However this may be, the bones just 

 described are lumbar vertebrae (Lat. lumbus, the It. in : where 

 such vertebrae are situated in man and other mammals) ; which 

 certainly possess abortive ribs in some cases. On successive 

 lumbars the cross-bars, whatever their nature, commonly slip 

 lower and lower downward (belly- ward) on the vertebral bodies, 

 till the last ones are quite down to the level of the ventral 

 aspect of the centrum ; these are also commonly the stoutest, 

 most directly transverse, and most nearly horizontal of the series 

 of processes, abutting against the ilia a little in advance of the 

 socket of the thigh bone. This ends a series of consolidated 

 "sacral" vertebrae which are termed collectively " dorso-lumbar," 



Fig. 57. —The "sacrum" of 

 ii young fowl, seen from below, 

 nat. size ; after Parker. (II, dor- 

 solumbar series, whereof the first 

 is dorsal proper, the next three 

 are lumbar ; x, the sacral series 

 proper, or true sacrum, consist- 

 ing of five vertebrie ; c, the uro- 

 sacral series, being those caudal 

 vertebra;, six in number, which 

 anchylose with one another and 

 with the sacrum. 



