Proc. Roy. Socy. of Edin .] 
[Vol. XXVII. 
Fig. 5. — From a vertical section of the Cranium of a Rat 
set. three months, fed on bread-and-milk. 
Note the well-developed frontal hone. Cf. fig. 6. 
Fig. 6. — From a vertical section of the Cranium of a Rat 
set. three months, fed on ox-flesh. 
Note the imperfect development of the frontal bone and the increase 
in the size of the medullary cavity. The mucous membrane of 
the nose is in a state of catarrh. Cf. fig. 5. 
Dr Chalmers Watson. 
[Plate III. 
