ON THE BONES OF ANIMALS, 



41; 



union of fractured bones, or the exfoliation of a part of a bone, For the proceflcs 



*re procefles requiring a coniuierahle length of lime for their gfe^eft^re/i^ 



performance. In Dr. McDonald's experimenl?, the formation flow. 



oi' a regenerated bone required nearly lix weeks; but during 



the fame fpace of time, the bones of the fame animal would 



be renewed fevera! times, if the common explanation of the 



communication and difappearance of the tinge of madder were 



well founded. From thefe circumRances, I am led (o believe 



that the appearances produced by the exhibition of madder, 



require another mode of explanation. That which I have to 



offer is not liable to the fame objeftions, and is ftrongly fup- 



ported by comparative experiments. 



It was obferved by Du Hamel, in his experiments, that the A fimple cxpU- 

 bones of animals which had been deeply tinged by madder, "„ e""pefi^ut, 

 by long expofure to air loft their colour and became white. — 

 It was this fad which fuggefted to me a (ioiple explanation of 

 the procefs. It occurred to me, that if any one of the com- 

 ponent parts of the blood naturally exerted a ftronger attrac- 

 tion for the colouring matter of madder, than the phofphate 

 of lime, it might be deprived of the tint by a chemical power. 

 In order to prove this, as far as I could by experiment, I took J^^ ferum of 



, ... , ,• , I- ,■ • I • TA 11 1 olood has a 



one dram ot the phofphate of lime tniged, as in Dr. Kuther- ftronger attrac- 



ford's exi»eriment, and expofed it for half an hour to the ac- tion for the 

 tion of two ounces of freOi ferum, at the temperature of 98 ^f n^a;]"/^^ than 

 degrees. By this operation, the ferum gradually acquired a phofphate of 

 red tinge, whilft the phofphate of lime was proportionably '"^^ ^*' 

 deprived of colour. In a comparative experiment, a fimilar 

 quantity of tinged phofphate of lime was expofed to the a6lion 

 of diftilled water under fimilar circumftances; but no change 

 took place. The knowledge of this flrong affinily in the fe- 

 rum for colouring matter, affords an eafy and fimpie explana- 

 tion of the effects of madder on the bones, upon the principle 

 of chemical attradion. 



Thus, when an animal has madder mixed with its food, the Hence the bones 

 blood becomes highly charged with it, and imparts the fuper- much madder 

 abundant colouring matter to the phofphate of lime, contained is in the fyftem, 

 in the bones already formed ; as it circulates through them and ^^^ fer^um when 

 moiftens them throughout. But as foon as an animal has the quantity be- 

 ceafed to receive the madder, and the blood is freed from the *^'''"^^ ^^^** 

 colouring matter by the excretions, the ferum then exerts its 

 fuperior altra<5tion, and by degrees entirely abftracls it from 

 ibe 



