442 Chapter XIV 



variability in the protective power of the blood of persons who had 

 recovered from cholera. We were able to demonstrate its presence 

 in rather more than 58 per cent, of these cases. Sometimes this 

 power was almost as marked as in the example given by Lazarus, 

 whilst in others it was very feeble, often even nil. We were unable 

 to demonstrate any relation between the gravity of the disease and 

 the strength of the protective power of the blood. Thus, in a mode- 

 rately severe case of cholera, a very small quantity of serum (0*001 c.c.) 

 was sufficient to protect the guinea-pig from fatal cholera peritonitis, 

 whilst in another, an extraordinarily grave case, even a quantity of 

 2 c.c. was incapable of producing the same effect. In these two cases 

 the blood had been withdrawn at the corresponding period after the 

 commencement of the disease (seventy-third and seventy-fifth days). 

 Sobernheim {l.c) found the protective power of the serum most 

 marked in a person who had cholera vibrios in his normal dejecta, 

 but who was always in good health and was only examined because 

 he was living with cholera patients. 



All these observations point to the fact that neither recovery from, 

 nor immunity against, cholera can be regarded as a consequence of 

 the protective power of the blood. This power does not manifest 

 itself until some time after complete recovery has taken place, and 

 then disappears too soon, that is to say at a moment when acquired 

 immunity ought still to be maintained. On the other hand, the 

 irregularity in the protective power of the blood indicates that this 

 humoral property is something secondary. Since Asiatic cholera is an 

 intoxication by the cholera toxin, we can readily understand that the 

 protective power, resulting from the invasion of the living parts of 

 the organism by the vibrios, should here play a part of little import- 

 ance. We know already that this power is due to the presence of 

 substances manufactured by phagocytic elements, placed in contact 

 [484] with vibrios. In the experimental infection of rabbits by the cholera 

 vibrio, as demonstrated by Pfeiffer and Marx, the cells of the spleen, 

 of the lymphatic glands, and of the bone-marrow, produce the pro- 

 tective substances. We have no idea of the source of these substances 

 in Asiatic cholera in man. 



Asiatic cholera, being an example of intoxication of intestinal 

 origin, it might be supposed that the antitoxic power of the body 

 fluids should be specially manifested after recovery has taken place. 

 On this point our knowledge is as yet very imperfect, because it was 

 not until after the end of the last epidemic of cholera that Ave learnt 



