DEVELOPMENT OF BOXE OUT OF PERIOSTEUM. 4-67 



from the medulla, a compact substance is produced, like 

 that of the cortex, which is always characterized by the 

 lamellar deposition of osseous tissue in the previously ex- 

 isting medullary spaces. The original bone is always 

 pumice-stone-like, and porous ; its porosities become filled 

 by the subsequent development of osseous lamellae from 

 the layers of the marrow, the process continuing until 

 the vessel, which does not admit of ossification, alone re- 

 mains. 



Now with regard to the development of bones in thick- 

 ness, the process is in itself much simpler, but it is also 

 at the same time very much more difficult to see, be- 

 cause ossification here proceeds very rapidly, and the 

 proliferating periosteal layer is so thin and delicate, that 

 extremely great care is required in order to catch sight 

 of it at all. Pathology furnishes us with an incompara- 

 bly better opportunity for studying the process than 

 physiology. For it is just the same whether the bone 

 grows physiologically in thickness, or pathologically in 

 consequence of periostitis ; the difference is only one of 

 quantity and time. 



When fully developed, the periosteum consists for the 

 most part of a very dense connective tissue which con- 

 tains an extremely large quantity of elastic fibres, and 

 in which the vessels ramify, before they pass on into 

 the cortex of the bone itself. Now when the growth 

 of the bone in thickness commences, we see that the 

 most internal, vascular layer (of the periosteum) in- 

 creases in thickness and swells up, and then it is said an 

 exudation has taken place, it being taken for granted, 

 that every swelling proves the occurrence of an exuda- 

 tion, and that the exudation here lies between the peri- 

 osteum and the bone. But if you set to work and 



in other words, soft, uncalcified, osseous tissue. From a MS. Note by the 

 A uthor. 



