FOR MICROSCOPICAL EXAMINATION. 123 



of the layers of dentine, form elegant patterns when seen in 

 section. 



From their comparative softness, fish teeth can be readily re- 

 duced upon a common gi-indstone and hone, to a degree of suffi- 

 cient thinness for examination. Even the fossil ones may be 

 treated in the same way with success. But by slicing thick 

 ones, such as Ptychodus, Cochleodus, Myliobatis, &c., .on a 

 lapidary's wheel, much labour and material are saved. 



Both recent and fossil specimens may be mounted in Canada 

 balsam. Some of the recent are evidently improved by first stain- 

 ing them in carmine, and some mounted in glycerine show the 

 vascular system beautifully distinct. 



At the close of the paper the President observed that he had 

 paid a good deal of attention to the Microscopic structure of bone, 

 and could not admit that the best method of preparing such was 

 by grinding down. In his opinion, this method in many cases filled 

 up the cavities with debris, and thus obscured much which ought 

 to be seen. Under favourable circumstances, it might perhaps 

 answer for dry bones, where the form of the lacunae and canaliculi 

 was all that was required. But if we take a fresh bone, and with 

 a strong, sharp knife cut off a very tiny slice, which could be 

 easily done, and then immerse it in carmine dissolved in ammonia, 

 the ammonia being first neutralised by acetic acid, the walls of the 

 vessels w^hich penetrate the lacunte and canaliculi are by this means 

 stained crimson, and thus the true structure of bone is rendered 

 visible. 



