MEDULLARY MEMBRANE OR INTERNAL PERIOSTEUM. 33 



This membrane covers the whole bony surface, except those 

 parts which are invested by cartilages, and the capsular liga- 

 ments of joints, those which are occupied by the insertion of 

 tendons and ligaments, and the bodies of the teeth. It appears 

 most intimately connected with the surfaces of spongy oones, 

 and the extremities of the long bones. In a sound state it has 

 very little sensibility ; but in some cases of disease it appears to 

 be very sensible ; of course it must be supplied with nerves, 

 although several expert anatomists have declared they could not 

 trace them. 



It is probable that the principal use of the periosteum is to 

 transmit vessels to the bones for their nourishment ; but death or 

 exfoliation of the surface, does not always take place when the 

 periosteum is removed from a portion of bone.* 

 This membrane presents a polished, pearly white appear- 

 ance, when examined in the recent bone. It has received 

 different names according to the parts which it covers, though 

 its structure is nearly uniform throughout. Thus, when it 

 covers the exterior surface of the bones of the cranium it is 

 called pericranium ; when it covers the cartilages, perichon- 

 drium ; and when it covers the bones with the exception of 

 those of the head, periosteum. 



In infancy the periosteum is soft, thick, and spongy, and 

 may be readily separated from the bones. In adult life it is 

 more firm and compact, and is often so intimately united to the 

 bones as to be detached with difficulty from them. In old age 

 it is extremely dense, and becomes not unfrequently ossified at 

 its internal surface. Its vascularity, which is at first rather 

 obscure, also gradually increases as life advances, but in old age 

 it again diminishes.f 



Of the Internal Periosteum or Medullary Membrane. 

 This membrane is particularly well marked in the cavities 



* Dr. Physick thinks that the periosteum frequently prevents the bones from 

 participating in contiguous disease, as the pleura turns off an abscess inthe parie- 

 tes of the thorax from its cavity, or the peritoneum from the cavity of the 

 abdomen. 11. 



f Anat. Phys. and Diseases of Bones and Joints. By S. D. Gross, M. D. 



