HISTOLOGICAL DEMONSTRATIONS. 85 



glass, and tear off a few of the peripheric lamellae. After 

 this some of Sharpey's fibres may be found isolated, by 

 being torn out of their sockets. 



d. The periosteum. In the adult animal the periosteum 

 consists simply of fibrous tissue, with a connective tissue 

 corpuscle here and there imbedded amidst the fibres, or 

 in contact with the bone, but they are not readily seen 

 unless the section be exceedingly thin and stained. In 

 another preparation it will be seen that the periosteum of 

 the young bone has a very different appearance. The 

 contents of the cancelli and of the Haversian canals will 

 also be better seen in other preparations. 



124. Development of Bone. Young periosteum. 

 (H.) Examine a T. S. long bone from kitten at birth, 

 softened in the chromic and nitric fluid, or in picric acid, 

 and stained with picro-carmine. A layer of nucleated cells 

 (osteoblasts) is found under the fibrous tissue of the perios- 

 teum close to the bone. On carefully examining the whole 

 thickness of the periosteum, it may be seen that these cells 

 are proliferations from connective tissue corpuscles. They 

 may be traced into the Haversian canals, and through these 

 into the cancelli. Everywhere they are in contact with the 

 bone. These osteoblasts ultimately become the bone cells ; 

 the matrix of the bone grows around and encloses them. 

 The manner in which the canaliculi are formed is disputed ; 

 some maintaining that they are mere spaces left in the bony 

 matrix during its growth. It may be seen, however, with 

 (H.), and still more clearly with a power of 1000 diam., 

 that the osteoblasts have often very distinct processes 

 before they are included in the bone. This preparation 

 shows a very delicate fibrous tissue in the cancelli and in 

 the Haversian canals, through which it is continuous with 

 the periosteum, capillaries and larger vessels may also be 

 found in the cancelli, Haversian canals, and in the perios- 

 teum, especially in its inner layer. 



125. Intra- cartilaginous Formation of Bone 

 V. S. bone and articular cartilage from softened bone of adult 

 cat, prepared as directed in 15. Treat in the same 

 manner as the softened bone ( 123). 



