462 ANATOMICAL AND PATHOLOGICAL OBSEEVATIONS. 



The hard part of the osseous texture, considered in a long- 

 bone, presents four surfaces, all communicating with one an- 

 other, a periosteal or external, a medullary or internal, a 

 Haversian or intermediary, and a corpuscular or canalicular. 

 The periosteal surface communicates with the Haversian in 

 three ways : by those Haversian canals which open in it ; by 

 the canal for the medullary artery gradually subdividing and 

 diminishing till it breaks up into arterial Haversian canals ; 

 and by the more numerous canals for the veins, principally 

 met with at the extremities of the bone. The medullary 

 surface is to be considered as a portion of the Haversian, 

 having been formed by the enlargement, and subsequent 

 blending of neighbouring Haversian canals into medullary 

 cavities and cancelli. The canalicular or corpuscular surface 

 forms the walls of the innumerable corpuscles and canaliculi, 

 and communicates by the latter with the Haversian, medullary, 

 and less freely with the periosteal surface. 



The compact osseous substance, in which the corpuscles 

 and their canaliculi are situated, is not homogeneous in 

 texture. It consists of cells filled with bony substance, 

 ossified or calcified primordial cells. 



The soft part of the true osseous texture is not con- 

 tinuous like the hard, but is divided, as has been stated, into 

 as many portions as there are corpuscles in the bone. Each of 

 these portions consists of a little mass of nucleated cells of 

 great transparency. They do not appear to extend along the 

 canaliculi, but to be confined to the cavity of the corpuscle. 



These two parts, the hard and the soft combined, con- 

 stitute the true osseous texture. They differ from one an- 

 other only in this, that the cells of the one are ossified, those 

 of the other retain their original delicacy and softness. The 

 masses of soft cells in the corpuscles, I am inclined to 

 consider as the nutritive centres, germinal centres, or germinal 

 spots of the texture. These centres are the source of all the 



