76 DENNIS, ON THE MICROSCOPIC 



Addenda. 



The general truth of ray observations may be easily tested 

 by an examination of the bones of some of our common 

 animals, such as the hare, rabbit, squirrel, rat, mole, &c. 

 As mere microscopic objects, they will repay all the trouble ; 

 and the only apparatus required will be a fine saw, which is 

 best home-manufactured out of the main spring of a watch ; 

 a small hand grindstone ; a common slate hone ; and a piece 

 of leather to guard the fingers. Both a cutting and a writing 

 diamond will also be necessary. If the person is residing in 

 the country, let him take a walk to the first gamekeeper's 

 residence, and ask him to show him where he hangs the 

 vermin; or let him look out for a bush where the mole- 

 catcher hangs his moles ; or if he has rabbits for dinner, let 

 him save, to the utter astonishment of his servants, the bones. 

 The dainty morsels conveyed home, a rich mental feast is 

 soon prepared. Let me suppose the operator compares the 

 metatarsal bone of the rabbit or tlie hare with one of 

 the polecat or the mole. He v/ill find numerous Haversian 

 tubes in those of the rabbit and hare, not half so many in the 

 polecat, and quite a diflerent arrangement in the mole, with 

 complicated reticulations at the ends, and few Haversian 

 tubes, and of a peculiar character, in the shaft, quite distinct 

 from the rabbit, &c. If the whole under jaAV of the mole is 

 ground down, the Haversian tubes will be found to send up 

 a tree-like stem between the fangs of the molars, vrith. 

 branches across. The under jaw of the weasel is a very 

 suitable object to compare with the mole; and their distinc- 

 tive characters are easily recognised. The parietal bone of 

 the mole is also a nice object for comparison with that of the 

 Aveasel, and in the latter the Haversian tubes are much 

 reticulated, and compare more with those in the joints of the 

 hind metatarsal bones of the mole ; that is, they have that 

 complicated character. Now, the weasel is remarkable for a 

 very powerful muscular development in its head ; and so its 

 jaws show, in their microscopic characters, great strength of 

 action; and the play of the powerful temporal muscles is 

 registered in the disposition of the Haversian tubes, which 

 are more open in the mole, and less complicated in their 

 character. Let next he picked out one of the little vibrating 

 bones from the ear of the mole — it is itself almost microscopic, 

 but grind it down, and it will be seen to be marvellously full 

 of highly reticulated Haversian tubes; or let the lower 

 jaws of the rabbit, hare, squirrel, and rat, be taken, and let 



