1820.] Memoirs of tlie Literary Socieli/ of Manchester. 203 



contain 87 per cent, of oxygen gas. The impurity was probably- 

 owing to an accidental mixture of atmospheric air. Though 

 it is difficult at present to give any explanation of this singular 

 phenomenon, is it not possible that it may be somehow con- 

 nected with the extrication of oxygen gas when silver is placed 

 in contact with deutoxide of hydrogen ? 



When the silver or copper is covered with charcoal, and then 

 thrown in fusion into water, no gas is extricated from il. 



XVI [. ijbscrvaliuns on the Callous Tumour. By Mr. Kinder 

 Wood. — This is a name given to a tum ur which surrounds the 

 fractured part of a bone, when it is uniting together, and which 

 continues till the adhesion is complete, or till a perfectly bony 

 cement has perfectly united the two fractured poi'tioas of bone. 

 Mr. Wood's observations were deduced from fractures made on 

 the limbs of voung; rabbits. These were allowed to remain with- 

 out any attempt to replace the bones, and the progress was 

 ascertained by dissection at various distances of time after the 

 fracture. 



The fracture occasions a loss of vital energy, and about 12 

 hours elapse before any visible attempt at repairing the injury 

 commences. The ends of the fractured bones are at first rough, 

 which occasions them to injure the muscles in their neighbour- 

 hood. The first change that takes place is the effusion of a 

 quantity of coagulable lymph from the internal membrane of the 

 bone. By this, the fractured faces are covered, and made beau- 

 tifully smooth. This lymph adheres firmly to the internal 

 periosteum, and obviously proceeds from it. 



About 36 hours after the fracture most of the extravasated 

 blood is absorbed. The external membrane of the bone becomes 

 thickened and vascular, a quantity of coagulable lymph exudes 

 from this membrane and from the muscles, and surrounds and 

 envelopes the ends of the fractured bone. It is this exudation 

 which constitutes the callous tumour. It becomes gradually 

 firmer and firmer, the external periosteum of the bone below it 

 is destroyed and removed, and a new periosteum formed which 

 encloses the callous tumour, and fixes it firmly to the bone. 

 The earthy salts are slowly deposited in this tumour, and in 

 proportion as the bone acquires strength, the tumour is dnui- 

 nished ; but a long time elapses before it disappears. 



When the external periosteum of the bone is destroyed, no 

 callous tumour is ibnned, the ends of the bone lose their 

 vitality, and must be removed before the fracture can be healed. 

 When the internal periosteum is injured or destroyed while tlie 

 outer remains, the callous is formed as usual ; but the bones do 

 not unite, because their asperities are not removed by the usual 

 deposition of coagulable lymph. The consequence is, that the 

 callous gradually assumes the form of a capsular ligament, the 

 inner periosteum gives out a glairy Huid resembUng synovia, and 

 an artificial joint is formed. 



