?94 Dr. Hancodc on the Composition Qf the Fin Rays 



^ In respect to their extreme density and hardness they also 

 shpw a very great disparity, but this need not here be insisted 



That such are the positions of the organs of hearing in fishegj 

 i»e. within the cavity of the cranium (along with the brain), 

 there can scarcely remain a doubt, although it appears to have 

 been disputed by no less a naturalist than M. de St. Hilaire. 

 Of this I have been informed by Mr. Yarrell, who will, ere 

 long, it is to be hoped, instruct us with the result of his more 

 exact investigations on the mysterious points of comparative 

 anatomy here referred to. ^aoiiilcf 



The bones found within the cavity of the cranium of the 

 manati are undoubtedly the same as those alluded to by Mr. 

 Gray in the first edition of his Pharmacology. He observes, 

 p. 105, " Manati stone, lapis manati. The teeth of the sea- 

 cow ;" and Blumenbach doubtless alludes to this bone also in 

 his Manual, p. 283, where he observes, that *' the hard bony 

 substance which was formerly very erroneously called lapis 

 manati, or tiburonis, is merely the tympanum and bulla ossea 

 of the whale." lO 



. It would hence appear, that this learned naturalist had 1*0 

 knowledge of, or had mistaken, this stone or bone of peculiar 

 hardness and density, possessing the highest celebrity among 

 |;he Indians and natives over all Guiana and the West India 

 islands, for their reputed virtues in convulsions, colic, dis- 

 uria, &c. ^D 



Air-Bladder. ^^^^^^ 



Jhe term air-bladder seems very proper, but sound, on the 

 contrary, if signifying any thing connected with the bottom, is 

 surely the reverse of propriety. 



It is certain that the air-bladder of fishes assists them in 

 rising in the water, and hence ought to be regarded as, in some 

 measure, auxiliary to motion ; but the idea of its contributing 

 to progression through this element is contrary to reason, for 

 there can be no necessity for it in a horizontal movement, the 

 great power of the tail and fins in fishes, and their bodies 

 being naturally little, if anything, more than the specific 



