244' Prof. Draper on the Existence and Effects of Alloiropism 



with the oxygen it has thus obtained, the arterial blood passes 

 to all parts of the system ; and now arises that striking but 

 all-important physiological fact, that it does not attack indis- 

 criminately all those parts of the soft solids which it first en- 

 counters, but proceeding in a measured way, exerts its action 

 on such particles alone as have become effete, and accomplish- 

 ing the great process of interstitial death, resolves those par- 

 ticles into other forms, so that they can be eliminated from 

 the system by the lungs, the kidneys, and the skin. 



Now why is it that things proceed in this way ? What is it 

 that regulates this interstitial death ? Why is one atom pre- 

 served and another surrendered ? 



It is upon these obscure points that the recent discoveries 

 in allotropism shed a flood of light. 



The three leading neutral nitrogenized bodies, fibrine, 

 albumen and caseine, are characterised by exhibiting allotro- 

 pism in a most remarkable degree, and that in a double sense. 

 1st. Though so different from one another in their physical 

 and chemical relations, it is admitted on all hands that they 

 are mutually convertible; the albumen of the egg, during in- 

 cubation, gives rise to fibrine and other allied bodies ; from 

 caseine, in the milk with which the young mammalia are 

 nourished, the albuminous and fibrinous constituents of their 

 systems arise; the nurse fed on fibrine and albumen secretes 

 caseine from the mammary gland. Indeed there is no more 

 reason to regard these three bodies as essentially distinct sub- 

 stances, than there is to apply the same conclusion to char- 

 coal, plumbago and diamond. Between the two cases there 

 is the most complete analogy; and if charcoal, plumbago and 

 diamond, are merely allotropic forms of one substance, the 

 same holds good for fibrine, albumen and caseine. But 2nd, 

 each of these three compounds betrays a disposition under 

 trivial causes to assume new forms; as with silicic acid so with 

 fibrine, there are two varieties, one soluble in water, the other 

 not. A difference of a few degrees of heat turns transparent 

 albumen into the porcellanous variety, and analogous obser- 

 vations might be made respecting caseine. 



It may therefore be asserted that these proteine bodies ex- 

 hibit a propensity to allotropism in a far more remarkable 

 manner than any other substances known ; not only passing 

 indiscriminately into one another, but also exhibiting special 

 variations under the influence of the most trivial causes. 



And now we may recall the fact, that of the agents which 

 in the inorganic kingdom bring about these changes, the im- 

 ponderable principles are pre-eminent. I transfer this obser- 

 vation to the case of organized beings, and infer that the ner- 



