34 MEDULLARY MEMBRANE OR INTERNAL PERIOSTEUM. 



of the long bones, where it forms a thin, delicate, pellucid, 

 vascular membrane, lining the sides of the cavities of the reticu- 

 lated tissue, in which it forms vesicles, that contain the marrow. 

 The lining membrane of the cells in the spongy portion of 

 the bones is still more delicate in its structure, and more difficult 

 of demonstration, and has been supposed by many anatomists 

 to be formed only from the coats of the blood-vessels which 

 anastomose thousands of times with each other in the interior 

 of these bones. Its office, however, is precisely similar to that 

 of the membrane in the cavity of the long bones, to lodge the 

 fatty or medullary matter which is furnished by exhalation. 

 It is very inflammable/ burning with a beautiful blue tinge, and 

 an oily disagreeable odor, fluid during life, but presents itself 

 after death, under the form of brilliant granules of solid fatty 

 matter. When death has taken place from some wasting 

 disease as dropsy or consumption, the fat is removed by 

 absorption, and its place is supplied by a watery fluid which 

 renders the bones less greasy and more valuable as cabinet 

 preparations. This medullary substance as has been before 

 observed is also found with the vessels in the canals of the com- 

 pact portions of bone< 



At the extremities of the long bones, the formina for the 

 transmission of the blood-vessels and fibres are much larger 

 than they are in the middle ; but there is an oblique canal near 

 the middle of these bones, which transmits vessels to this 

 membrane in the interior of the bones called nutritious or 

 medullary. 



The surface of the internal cavities and cells of bones it will 

 then be seen, is lined by a membrane more delicate and more 

 vascular than the periosteum, which contains the medullary 

 matter that is always found in their cavities. [This is the* 

 internal periosteum or the medullary membrane of the bones. 

 M. Portal denies that it exists as a distinct membranous sac, 

 but asserts, that it is derived from the envelop of the vessels 

 which is sent in along with them from the periosteum.] 



It has been said that in some circumstances this membrane 

 has had great sensibility, but the- reverse is the case in com- 

 mon. 



