IN THE VERTEBRAL COLUMN OF CARTILAGINOUS FISHES. ($53 



I have not had an opportunity, as yet, of examining minutely the vertebral 

 column of the Lamprey, Pride, or Hake, the fishes which belong to the order 

 Cyclostomi ; but I have every reason to believe, that CUVIER and Dr GRANT are 

 correct in describing that column as consisting of a simple cartilaginous tube. 



As doubts may arise in the minds of some as to whether the osseous struc- 

 ture, which is above described, be really bone, or is simply condensed cartilage, 

 impregnated with earthy matter, I submitted it to a chemical examination, and 

 found it to yield in every case the same amount of earthy and of animal matter 

 as the most solid bones of osseous fishes. 



The osseous portion of the vertebrae of the Skate and Thornback Ray yielded 

 69.1 per cent, of earthy, and 30.9 of animal matters ; while the common cartila- 

 ginous skeleton of the same animals yielded only 35.0 per cent, of earthy, and 

 65.0 per cent, of animal matters. In the various species of Dog-fish or Sgualidce 

 examined, the proportions of earthy and of animal matters were found to be 

 within a fraction of those of the Rays, being, in the perfectly cleaned osseous 

 portion of the vertebrae, 68.9 per cent, of earthy, and 31.1 per cent, of animal 

 matters. In the osseous laminae of the vertebrae of the Squalls maximus or 

 Basking Shark, I found 71.5 per cent, of earthy matters, and 28.5 per cent, of 

 animal matters. These proportions are almost the very same as those which I 

 have found to be present in the perfectly cleaned bones of osseous fishes. The 

 earthy matters were chiefly composed of phosphate of lime ; carbonate of lime 

 was also present, but in very small quantity. 



CHEVREUL and MULLER are the only writers known to me who have pub- 

 lished analyses of the hard parts of cartilaginous fishes. CHEVREUL appears to 

 have undertaken the analyses for Baron CUVIER, and in 100 parts of the vertebra 

 of the Basking Shark (Squalus maximus), he found of azotized matter and of oil 

 64.85, sulphate of soda 18.59, chloride of sodium 13.62, subcarbonate of soda 

 2.00, phosphate of lime, &c., only 0.94. M. CHEVREUL thought that all these 

 soluble salts did not exist in a solid state in the cartilage, but were held in solu- 

 tion by the large quantity of water which recent cartilage contains, a quantity 

 amounting to no less than 90 per cent, of the weight of recent cartilage. 



It is quite apparent from this analysis, that M. CHEVREUL had only analysed 

 a portion of the enveloping cartilage of the vertebrae, and none of the truly osseous 

 structure which constitutes the essential basis of these bodies. The circumstance 

 of meeting with no phosphates proves this point : it does more ; it proves he had 

 not even included in his analysis any appreciable amount of the concentric osseous 

 plates of the vertebras. 



MULLER, on the other hand, analysed each of the varieties of cartilage which 

 he found present in cartilaginous fishes. In what he calls tubercular cartilage, 

 he found a small proportion of earthy matter, which chiefly consisted of the 

 phosphate of lime. In what he terms the ossified cartilage, he found in one case 



