256 



CONNECTIVE TISSUE. 



We observe in the middle of a layer of fibrous connective 

 tissue medullary corpuscles in longitudinal tracts (if cut trans- 

 versely) 5 we see that a number of such corpuscles coalesce in 

 order to be transformed into basis-substance, which almost 

 instantaneously becomes infiltrated with lime-salts. In this way 



FIG. 106. SKULL OF HUMAN EMBRYO, FOUR MONTHS OLD. 

 HORIZONTAL SECTION. CHROMIC ACID SPECIMEN. 



F. fibrous connective tissue of the pericranium ; M, medullary space, with central 

 blood-vessel ; , first-formed trabecula of bone ; O, row of osteoblasts ; C, medullary cor- 

 puscles of the inner pericranium, infiltrated with lime-salts. Magnified 500 diameters. 



trabeculae of bone, with large and irregular bone-corpuscles, are 

 formed between two layers of fibrous connective tissue, the 

 outer of which is the future external, the inner the future inter- 



