MORBID POISONS. 391 



If a body A, for example oxamide (a substance 

 scarcely soluble in water, and without the slightest 

 taste), be brought into contact with another com- 

 pound B, which is to be reproduced; and if this 

 second body be oxalic acid dissolved in water ; then 

 the following changes are observed to take place: — 

 The oxamide is decomposed by the oxalic acid, 

 provided the conditions necessary for their exercis- 

 ing an action upon one another are present. The 

 elements of water unite with the constituents of 

 oxamide, and ammonia is one product formed, and 

 oxalic acid the other, both in exactly the proper 

 proportions to combine and form a neutral salt. 



Here the contact of oxamide and oxalic acid induces 

 a transformation of the oxamide, which is decomposed 

 into oxalic acid and ammonia. The oxalic acid thus 

 formed, as well as that originally added, are shared 

 by the ammonia, — or in other words, as much free 

 oxalic acid exists after the decomposition as before 

 it, and is of course still possessed of its original 

 power. It matters not whether the free oxalic acid 

 is that originally added, or that newly produced; it 

 is certain that it has been reproduced in an equal 

 quantity by the decomposition. 



If we now add to the same mixture a fresh portion 

 of oxamide, exactly equal in quantity to that first 

 used, and treat it in the same manner, the same 

 decomposition is repeated ; the free oxalic acid en- 

 ters into combination, whilst another portion is 

 liberated. In this manner a very minute quantity 

 of oxalic acid may be made to effect the decomposi- 

 tion of several hundred pounds of oxamide ; and 

 one grain of the acid to reproduce itself in unlimited 

 quantity. 



We know that the contact of the virus of small- 

 pox causes such a change in the blood, as gives rise 

 to the reproduction of the poison from the constitu- 

 ents of the fluid. This transformation is not arrested 

 until all the particles of the blood which are suscep- 

 tible of the decomposition have undergone the met- 



