190 EXPLANATION OF THE PLATES. 



foetal marrow) and a great deal of free fat ; 7, angle correspond- 

 ing to position of a partition which has disappeared. 



FIG. V. Ossification "by periosteum (femur of a. newly 

 born infant). 1, Completely formed bone; 2, deepest portion 

 of the periosteum, in which some connective fibres and a large 

 number of plasmatic cells can be still distinguished ; of the lat- 

 ter, those nearest the bone begin to resemble bone corpuscles 

 in shape ; 3, superficial portion of periosteum, show few plas- 

 matic cells and numerous connective fibres ; 4, plasmatic cells. 



PLATE VII. 

 BONE, continued ; TEETH. 



FIG. I. Ossification of the os frontis at the margin of the 

 anterior fontanelle (from an infant four months old) ; 1, recently 

 formed bone ; 2, deepest portion of the periosteum ; 3, super- 

 ficial portion of the periosteum. The plasmatic cells, in this 

 specimen, give off distinctly marked branches. 



FIG. II. Ossification of cartilage, according to the most 

 generally received theory. 1, Capsule and cells, unaltered; 

 first appearance of the corrugation of the cell-wall ; 3, corru- 

 gation more marked ; 4 and 5, corrugation still farther advanced 

 and completed, resulting in formation of a bone-corpuscle. 



FIG. III. Transverse section of the canalieuli of the 

 ivory of a tooth. 1, Canalieuli; 2, their anastoniotic 

 branches ; 3, canaliculi divided a little obliquely. 



PLATE VIII. 



TEETH, continued. 



FIG. I. Incisor tooth of a child nine years old magnified 

 thirteen diameters. 1, Dental cavity ; 2, ivory ; 3, cementum 

 investing its root ; 4, enamel covering its crown. 



