34 Traces of Unity in the, &c. 



dugong, where both arches are very rudimentary, the 

 pelvic is the most so of the two, being represented by a 

 single ossicle without a trace of an appendage. What 

 particular ribs enter into the formation of these two 

 arches is a difficult question to answer. Owen is of 

 opinion that the scapular arch is formed by the ribs 

 belonging to the occipital vertebra ; and there is much 

 to say in favour of this view. For my own part, how- 

 ever, I am disposed to think that the scapular and 

 pelvic arches are formed, not of one rib only, but of 

 several, and that the rib-less spaces in the neck and in 

 the lumbar region are rib-less because the ribs belong- 

 ing to those parts have been gathered together and 

 modified, so as to form the scapular arch in the one 

 case and the pelvic arch in the other. And that it 

 may be so is, I think, made all the more probable by 

 the particular construction of that part of these arches 

 which corresponds to the costal cartilages, for how is it 

 possible to account for the division into coracoids and 

 clavicles in the one case, and into pubic and ischial 

 bones in the other, except upon the supposition that at 

 least two ribs enter into the formation of each arch, and 

 that the spaces between the coracoids and clavicles, and 

 between the pubic and ischial bones (the foramina ilii) 

 are in reality analogous to intercostal spaces ! 



In dealing with this matter now, however, I am wan- 

 dering beyond bounds. Indeed, all that I proposed to 

 do in this chapter is done already, for he must be very 

 sceptical who requires further proof before he is ready 

 to allow that distinct traces of unity are everywhere 

 present in the limbs of vertebrate animals. 



