INFECTIOUS DISEASES. 629 



more recent experiments of Wagner (1890). According to Canalis 

 and Morpurgo, pigeons which are enfeebled by inanition easily 

 contract anthrax as a result of inoculation. Arloing states that 

 sheep which have been freely bled contract anthrax more easily 

 than others ; and Serafini found that when dogs were freely bled, 

 the bacillus of Friedlander, injected into the trachea or the 

 pleural cavity, entered and apparently multiplied to some extent 

 in the blood, whereas without such previous bleeding they were 

 not to be found in the circulating fluid. Again, the simultaneous 

 injection of certain chemical substances may overcome the vital 

 resisting power of the tissues or fluids of the body in such a way 

 that infection and death may occur as a result of inoculations into 

 animals which have a natural or acquired immunity against the 

 pathogenic micro-organisms introduced. Thus Arloing, Corne- 

 vin, and Thomas have shown that rabbits succumb to symptomatic 

 anthrax when lactic acid is injected at the same time with the 

 bacillus into the muscles. Nocard and Roux have obtained the 

 same result by injecting various other substances, and their ex- 

 periments show that the result is due to the injurious effects of 

 the substance injected upon the tissues, and not to an increased 

 virulence on the part of the pathogenic bacillus. The experi- 

 ments of Leo are of a similar nature. By injecting phloridzin 

 into rats he caused them to lose their natural immunity against 

 anthrax. Certain anaesthetic agents have also been shown to pro- 

 duce a similar result. Platania communicated anthrax to immune 

 animals dogs, frogs, pigeons by bringing them under the influ- 

 ence of curare, chloral, or alcohol ; and Wagner obtained a simi- 

 lar result in his experiments on pigeons to which he had admin- 

 istered chloral. 



In view of the results of recent experimental researches which 

 show that, in certain cases at least, acquired immunity depends 

 upon the formation of an antitoxine in the body of the immune 

 animal, we are convinced that the theory of immunity under dis- 

 cussion, first proposed by the writer in 1881, can not be accepted 

 as a sufficient explanation of the facts in general. At the same 

 time we are inclined to attribute considerable importance to ac- 

 quired tolerance to the toxic products of pathogenic bacteria as 

 one of the factors by which recovery from an infectious disease is 

 made possible, and subsequent immunity established. Of course, 

 when we ascribe immunity to the " vital resistance " of the cellular 

 elements of the body, we have not explained the modus operandi 

 of this vital resistance or " reactive change/' but have simply 

 affirmed that the phenomenon in question depends upon some 

 acquired property residing in the living cellular elements of the 

 body. We have suggested that that which has been acquired is a 

 tolerance to the action of the toxic products produced by pathoge- 



