174 MODUS OPERANDI OF 



79. It is obvious, that all compounds, of what- 

 ever kind, which are present in the capillaries, 

 whether separated there, or introduced by endos- 

 mosis or imbibition, if not altogether incapable of 

 uniting with oxygen, must, when in contact with 

 the arterialised globules, the carriers of oxygen, be 

 affected exactly in the same way as the solids form- 

 ing part of living organs. These compounds, or their 

 elements, will enter into combination with oxygen, 

 and in this case there will either be no change of 

 matter, or that change will exhibit itself in another 

 form, yielding products of a different kind. 



80. The conception, then, of a change in the two 

 qualities of the blood above alluded to, by means of 

 a foreign body contained in the blood or introduced 

 into the circulation (a medicinal agent), presupposes 

 two kinds of operation. 



Assuming that the remedy cannot enter into any 

 such chemical union with the constituents of the 

 blood as puts an end to the vital activity ; assuming, 

 further, that it is not in a condition of transforma- 

 tion capable of being communicated to the consti- 

 tuents of the blood or of the organs, and of continu- 

 ing in them ; assuming, lastly, that it is incapable, 

 by its contact with the living parts, of putting a 

 stop to the change of matter, the transformation 

 of their elements ; then, in order to discover the 

 modus operandi of this class of medicinal agents, 

 nothing is left but to conclude that their elements 

 take a share in the formation of certain constituents 



