SKELETON. 



651 



we shall have produced such a vertebra as 

 Jig. 477. or 478., which, composed of the ele- 

 ments 1, 4,5, happens in the tail of cetaceans, 

 saurians, fishes, and many species of even the 

 quadruped mammalia. There are chevron os- 

 sicles developed on the caudal vertebrae of the 

 quadrumanous species. The caudal vertebra 

 (Jig. 477.) having the chevron bones (4) and 

 inferior spinous process (5) appended to it, 

 is taken to be the typical vertebra by all ana- 

 tomists. They regard it as containing all 

 the elemental parts proper to all vertebras, an 



opinion, the error of which I shall not 

 here stay to point out, if it be not already 

 demonstrated by what I have elsewhere 

 spoken. Taken as quantities of osseous 

 form, it would be as impossible to distinguish 

 the same parts in such a " typical " vertebra, 

 as either 9, 10, or 11, /g. 479., and that 

 which stands at the thoracic region of spinal 

 series, as it would be to read the quantity 

 a b and a+b as equal. In Jig. 479., which 

 represents the cetacean loins, it will be seen 

 that the thoracic ribs 1, 2, 3, hold serial order 



Fig. 479. 



The lumbar region of the Dugong's skeleton, 

 Showing a serial degradation of the ribs into the chevron bones. 



with the costiform pubic arch 7, and that this 

 series is continued into the lesser quantities 

 of chevron bones 9, 10, 11. This serial order 

 indicates the homology of these several struc- 

 tures. 



PROP. XXXVII. The sternal median line 

 ranges from the maxilla to the pubic bones of 

 the abstract archetypal skeletal fabric. In 

 order to comprehend the truth of this propo- 

 sition, the reader will have to exercise his 

 mental as well as his bodily vision. He will 

 have to expand his view over a large number 

 of facts, and to compare these one with 

 another, and sum together all the evidences, 

 making them demonstrate the generalization 

 which I here propose to establish. The ab- 

 stract idea which general comparison has fur- 

 nished me with respecting the sternal median 

 series of osseous pieces, I shall endeavour to 

 develope in the reader's mind, after the same 

 manner in which it was furnished to my own ; 

 and comparison of anatomical facts shall be 

 my instrument. 



When I compare all skeletal fabrics by the 

 sternal apparatus, I find that such an infinite 

 variety marks them in respect to this par- 

 ticular, that it would take a long and busy 

 lifetime to make a record of one half of those 

 varieties ; and, after all, it is most true, that 

 such- record would not be worth one jot to 

 science, since it would leave us in the end 

 no better informed as to the law producing 

 this variety, than when we first began. The 

 one great fact which I shall remark upon 

 in reference to the sternal apparatus is, 



that it is a part which varies not only in 

 several species but even in the one species, 

 and that it is a structure the most indeter- 

 minate and indefinable of all those consti- 

 tuting the osseous skeleton. It is produced 

 of variable lengths in the human body, and in 

 every other animal species regarded per se. 



Now, assuming that the interpretation of 

 sternal variety, and not the enumeration of it, 

 is the sovereign and paramount object of com- 

 parative research, I here venture to affirm, 

 that there is no other mode of accounting for 

 this variety, as it appears already created, 

 or of interpreting the process which has 

 yielded it, excepting that of regarding every 

 variety of sternal apparatus as being propor- 

 tional lengths cut from a whole linear sternal 

 quantity, drawn in continuous order through 

 the median line of the fore aspect of the 

 animal fabric from end to end. The reasons 

 which lead me to adopt this reading of the 

 source of sternal variety are as follow. 



When I examine the human skeleton as a 

 form isolated from all other forms of the 

 four higher classes of animals, I find the sternal 

 series of osseous pieces extending through that 

 region of the median line in front where the 

 fully produced ribs meet it and enclose 

 thoracic space completely. This costo-sternal 

 junction happens generally between the seven 

 first ribs and the sternal apparatus. It is 

 owing to this sternal union of these seven 

 ribs, that the human anatomist terms them 

 " true ribs." The five succeeding costal pairs 

 he terms " false ribs," because they are 



