344 THK MECHANICAL FUNCTIONS. 



When madder was alternately given and withheld 

 during certain regular periods, in a young animal, 

 Duhamel found that the bones which had been 

 growing during the whole of that time, were com- 

 posed of alternate layers of a red and white colour ;* 

 a result which, as Flourens has lately shown, is 

 owing to the particles of madder, which were 

 mingled with the circulating blood, adhering to the 

 phosphate of lime while it was deposited to form 

 each new layer of bone : and the reddened layer 

 thus formed being afterwards covered over and 

 concealed by the next superposed layer, which 

 being deposited at a later period, when no madder 

 was supplied, had the white colour natural to bone. 

 So rapid is the colorific operation of madder, that 

 Flourens obtained, in the course of five hours, a 

 perceptible tinge from only six grains of madder, 

 given to a young pigeon during a single meal.f 



but merely that the colouring particles of madder, when present in 

 the blood, readily attach themselves to the particles of phosphate of 

 lime which are deposited in the bones. Mr. Gibson had inferred, 

 from some experiments which he made, that the colouring matter so 

 deposited is again removed from the bones, in consequence of its 

 affinity with the serum of the blood, when that fluid is restored to 

 its usual state by the discontinuance of the supply of madder. 

 ^Memoirs, of the Lit. and Phil, Soc. of Manchester. Second series, 

 i. 146.) But the recent experiments of Mr. Paget throw much 

 doubt on the correctness of this theory. (London Medical Gazette, 

 XXV. 277.) 



* Mem. Acad. Sc. 1739. 



f Comptes Rendus, x. 143 and 305. 



