OF COLYMBUS TORQUATUS. 145 



approximation of its articulations with the body and transverse process of the first dorsal 

 vertebra In fact there is only left between them a small oval foramen. 



The six succeeding ribs are the true dorsal ones, and present the characters of the ribs 



ix succeeamg nus mc mc Ui ^ *^^ — ~, r 



Their necks are long and slender, and increase in length from before backwards ; 

 they support a head which is but very slightly enlarged. The tubercles of the ribs are 

 very large and stout. In fact, these broad, flattened, transverse processes seem almost to 

 form the true termination of the ribs, from which the neck and head proper seem but 

 offsets The ribs are very flat antero-posteriorly, and scarcely seem to grow narrower as 

 they 'approach the transverse processes of the vertebra. But from their inner surfaces 

 there commences, at some distance from the vertebra, the projecting ridge which is to be 

 continued beyond the transverse processes to form the neck and head ,...,,., 



As usual, the ribs consist of vertebral and sternal portions, movably articulated with 

 each other. Both of these portions grow successively longer from before backwards ; but 

 Z sternal portions much more rapidly than the vertebral. Thus while the ^sterna portion 

 of the second rib is barely three fourths of an inch long, that of the seventh is fully three 

 inclie The angle at the junction of these two portions, of course, varies with every stage 

 of an insn ™t on and expiration; but at any given moment the angles become successively 

 l^ZtZ before backwards, - from the increasing length of the vertebral as well as 



th Tht™:es° which extend backwards and mesially from the dorsal ribs are well de- 

 veloped 1 extenc n. not only to the next rib behind, but over it to the succeeding inter- 

 lo Tie TheV are not straight, but curved, with their concavities towards he spine. 

 Th firsr ie that on the second rib, is the shortest, stoutest, and slightest ; the others 

 Lcome s U c^ssively longer, slenderer, and more curved, to the penultimate one but the last 

 become successively , proces ses are at first only hgamentously joined 



^tTr hTtyXt ea^uyU^ off from the lat f but with advancing 

 « it Ibably become more or less completely anchylosed. Each process is a so 

 :L eSd w th the rib from which it arises by a broad, dense, ^^o^^neo^ 

 tZoukr shape extending from its concave border to its own rib, and along the nb to 

 St hS^le of the spine ; and with the next succeeding rib by .— ^ 

 While each is thus firmly and unyieldingly connected wi h its own rib it nab - He a, 

 sist the intercostal muscles proper in drawing the succeeding rib towards itself, these slips 

 coiecivelv thus exerting no slight force in the respiratory movements of the thorax. 



The two ribs next succeeding the true dorsal, that is, the eighth and ninth pairs differ 

 frof^he cL^l in th i oril, winch is from the sacral vertebra, ; and in their great length 

 ^wt^i^B^Ue in their sternal portions, which are very nearly as long 

 afthehvertetr Tie angle between the two portions is also very acute ; bn the most 

 S^SLoce is, thafwith the last dorsal ribs the processes F*^^** 



■ w«i,, tint mi the ribs under consideration theie is not even 



terminate,— so completely tliat on uic nus 



™SSffi?££ tZZ£5™ fa, being unshed at either vertebra, or sterna, 

 J2£ It consist* merely of two extremely slender elastic bones, tanermg to a toe 

 point, somewhat large, and broader at ^*»t"Sfrttt 

 Tbe sternal portion is longer than the vertebral. Close by he J >" , , h ' 



sternal portion sends off from it* postenor border a small ahgbt procesj wfa c 

 directly ontwa,ds and forwards, lying parallel with the postenor borde, ot the nb, wn.c 



