AND DEVELOPMENT OF BONE. 201 



acunse and canallculi disappears, due to the fact that the organic 

 matter lining these lacunae and canaliculi has been dissipated by the 

 heat to which the section of bone has been subjected ; while, on the 

 other hand, if a similar section of bone be submitted to the continued 

 action of an acid, which shall dissolve the earthy matter of the bone, 

 we find upon microscopical examination that the lacunse and canaliculi 

 are still plainly visible, the organic matter which lined these spaces 

 not having been dissolved by the acid. In the long bone of an adult, 

 such as this femur, there exist a large central canal containing a 

 substance called marrow. It has been universally held up to the 

 present time that this canal is lined by a membrane continuous (by 

 means of processes traversing the substance of the bone) with the 

 external periosteum, this membrane is said also to be fibrous or of 

 precisely the same character as the external membrane, and by way of 

 distinction it is spoken of as the endosteum and sometimes as the 

 medullary membrane. Oilier, however, has called attention to the 

 fact that the very existence of this membrane is due solely to an 

 effort of the imagination, that in fact no such membrane exists. So 

 startling a statement on the part of Oilier, one so contrary to all that 

 we had hitherto learned from what were deemed reliable sources, 

 Duhamel, Troja, Flourens, Carpenter, Todd and Bowman, of neces- 

 sity required verification or negation. I have made such enquiry and 

 now submit to you a fresh bone from the ox, in which it is mani- 

 fest that no endosteum or medullary membrane can be shown to 

 exist. It is as important to remove error as to set forth truth, the 

 former is usually the more difiicult task, and no doubt our text books 

 will continue for many years to speak of the endosteum, its nervous 

 supply, &c., &c. 



The marrow or medulla of the shaft or diaphysis is found therefore 

 in this medullary canal unsupported by any investing membrane, but 

 frequently preserving the form of the canal in which it lies as in a 

 mould. 



Marrow consists essentially of cells and nuclei, with blood vessels 

 and a few fibres of areolar tissue, together with fat in variable quan- 

 tity. Marrow varies in appearance and structure according to the 

 age of the individual, being red in early life, and whitish or pale in 

 the adult. In old age the marrow consists largely of fat. It varies 

 in quantity in an inverse ratio to the thickness of the surrounding 

 bone, and takes the place of the osseous tissue removed by absorption. 



