306 Proceedings of Philosophical Societies. [Oct- 



many respects. Hence a great difficulty in generalizing that 

 branch of comparative anatomy, while it is easy to generalize 

 what relates to the animals with vertebras. But this difficulty 

 has suggested its own remedy. From the manner in which the 

 propositions relative to each organ are always grouped, M. Cu- 

 vier concludes that there exists among animals four principal 

 forms. The first is that which is known under the name of 

 animals with vertebrae ; and the three others are nearly similar 

 to it in the uniformity of their respective plans. The author 

 calls them mollusca, articulated animals, and radiated animals, 

 or zoophites. He subdivides each of these forms or branches 

 into four classes, from motives nearly similar to those which 

 have produced the four classes generally adopted among the 

 animals with vertebras. He has drawn from this disposition, 

 in some respects symmetrical, a great facility in reducing under 

 general rules the differences of organization. 



The comparison which the same author has made of the 

 osteology of the animals with vertebrae, has given him ideas 

 respecting the bony structure of the heads in this class, which 

 he has likewise presented to the Class. 



It had been for some time observed that the oviparous animals 

 with vertebrae, that is to say, birds, reptiles, and fishes, had cer- 

 tain common relations in their structure which distinguished 

 them from the mammalia. M. Geoffroy-Saint-Hilaire had even 

 presented some years ago an elaborate essay on the subject, of 

 which an account was formerly given, in which, among other 

 things, he had shown the identity of the structure of the heads 

 of oviparous animals, and the resemblance in the numerous 

 pieces which enter into their composition, with that of those 

 which we distinguish in the foetus of mammalia, where, as it 

 known, the bones are much more subdivided than in adults. 



M. Cuvier, adopting the views of M. Geoffroy, has tried to 

 determine in an accurate manner to what bone of the head of 

 mammalia corresponds each group of bones in the head of the 

 different oviparous animals ; and he conceives he has succeeded, 

 by joining to the analogy of the fcetus of the first the considera- 

 tion of the position and of the functions of the bones ; that is to 

 say, by examining what organs they protect, to what nerves and 

 vessels they give passage, and to what muscles they furnish 

 attachments. 



M. Jacobsen, Surgeon-Major in the armies of the King of 

 Denmark, has made known to the Class an organ which he 

 discovered in the nostrils of quadrupeds, with which no ana- 

 tomist seems to have been acquainted. It consists in a narrow 

 sack placed along the canal of the nose, defended by a cartila- 

 ginous production, covered internally by a mucous membrane, 

 doubled in part by a glandular tissue, receiving remarkable 



