136 WARFARE IN THE HUMAN BODY 



product of metabolism, though in one sense all such are 

 accidental. They may, however, have been provoked 

 by early embryonic substrates, and possibly subserve some 

 function. Onslow showed the skins of some coloured 

 rabbits contained a peroxidase, the cause of the colour. 

 The "adaptation" of the organism to any substrate part 

 of its environment must have been accidental to begin 

 with. Some cells had the power of response, and others 

 lacked it. This was so in the early stages of evolution, 

 and the same remains true now in every case of recovery 

 or death when an infection occurs. Protective, continued, 

 and successful reaction is adaptation. There are striking 

 analogies between such reactions, and those provoked by 

 drugs such as the metals. What for instance is the action 

 of arsenic ? It combines with the " complement " it 

 finds, and thus kills the epithelial cells which, according to 

 Filehne, are then digested. But killing a cell is combining 

 with it or part of it. Arsenic in lethal quantities is such 

 a protoplasm poison that there can be no swift reaction 

 process resulting in a catalyst which builds it up into a 

 harmless stable compound. In small continuous doses it 

 appears to produce fats, i.e. possibly a superabundance of 

 complement. Complement is thus a common bodily 

 product, not anything specially manufactured by specific 

 reactions, and therefore immunization must in many 

 cases mean a stimulation of the cells which produce com- 

 plement naturally. Immunity to arsenic, then, is most 

 likely due in great part to an increased production of 

 lipoids. But tolerance is immunity. Immunization is 

 thus a process as normal as digestion, save that all the 

 products are finally extruded as useless. The processes 

 leading to cure are of the same order. To give a homely 

 illustration we may say that if there is disturbance at a 



