EXPLANATION OF THE PLATES. 



PLATE XXXIII. 



STRUCTURE AND DEVELOPMENT OF BONE. 



Fig. 1. Parietal bone of human foetus, aged about two 

 months, magnified 30 diameters. 



Fig. 2. A portion of same, magnified 60 diameters, showing 



. the bone cells in process of development, some of 



which are seen lying loose in the spaces between 



the speculae, and which were destined, eventually, 



to become included in the ossific deposition. 



Eig. 3. Speculae of bone of a foetal humerus, showing the 

 gradual deposition of the bony matter in the meshes 

 of fibrous tissue, and altogether independently of 

 cartilage, magnified 350 diameters. 



Fig. 4. Lamina of a long bone, magnified 500 diameters, 

 drawn from a preparation kindly placed at the 

 author's disposal by Dr. Sharpey, by whom the 

 structure figured was first described. 



Fig. 5. Cancelli of one of the long bones of a human foetus, 

 magnified 350 diameters, showing the vast numbers 

 of granular corpuscles which the medullary cells of 

 bone of every age contain, but which are especially 

 abundant in foetal bones ; the larger cells are mag- 

 nified 750 diameters. 



Fig. 6. Cross section of the femur of a pigeon fed for 24 

 hours upon madder. This drawing was made from 

 a beautiful preparation belonging to Mr. Tomes, 

 and lent me by that gentleman. Magnified 220 

 diameters. 



