on tJie Bove.'f of Animals. 151 



Dr. McDonald's experiments were niade by 

 amputating the proper leg-bone of young 

 pigeons or chickens immediately above the 

 joint. The marrow was then extracted, and 

 the cavity, which contained it, filled with lint. 

 This process caused the death of the bone, and 

 the formation of a new bone surrounding that 

 destroyed, erisued. Immediately after the 

 experiment, the animal had its food mixed 

 with madder root, and the part was inspected 

 in different animals, at different periods. 



On examination tliree days afterwards, the 

 periosteum or enveloping membrane, was 

 found much thickened ; and underneath it a 

 gelatinous humour was effused, surrounding the 

 dead bone, and spotted with red osseous 

 nuclei ; proving that the regeneration of the 

 bone had commenced at this early period. 



In seven days the new bone was found soft 

 and flexible, not to be distinguished from 

 cartilage or gristle, except by the red tint the 

 madder had communicated to it ; yet the bone 

 destroyed Was not at all coloured, although 

 the other bones of the animal had acquired a 

 bright red. From this time the new bone 

 continued to encrease in hardness, surrounding 

 the old one like a sheath . The latter in about three 

 we^ks was so loose "as to be drawn out, and 

 in about fifteen days from, this Vime, the cavity 



