146 GENERAL ANATOMY. 



the medullary membrane is observable in rachitis which has 

 not been described. 



Among the affections peculiar to this membrane, spina ven- 

 tosa is the most remarkable. According to my own observa- 

 tions and those of several others, there are two and even three 

 distinct species of this disease. The considerable develop- 

 ment of the bone arises from the extraordinary growth of the 

 altered medullary membrane; but at one time the alteration 

 in the marrow consists in a carcinomatous degeneration in a 

 true, soft cancer; at another the tumour is fibrous and carti- 

 laginous: in some cases, particularly in children, the bone 

 enlarged in the middle, contains a highly vascular red sub- 

 stance whose nature has not been well determined this variety 

 is particularly observed in the bones of the metacarpus, of the 

 metatarsus and of the fingers. Spina ventosa particularly affects 

 the long bones of the limbs: in the femur it is generally the 

 inferior part of the bone that is diseased, in the humerus, the 

 superior. I have taken away the superior third of the fibula 

 in a young woman, in a case of spina ventosa, that had en- 

 larged the head of the bone to the size of the patient's fist. 

 Tumours of this nature have been described by Vignarous 

 under the name of bony steatoma, and by Sir A. Cooper under 

 that of medullary exostosis. 



