Immunity acquired by natural means 443 



how to prepare the toxin. In a case of cholera (M.S.), contracted 

 in our laboratory, the blood serum was examined to ascertain its 

 protective power and its antitoxic activity. This fluid, withdrawn 

 more than three weeks after the commencement of the disease, was 

 found to be protective only in a large dose (0'5 c.c.), in which dose 

 even the serum of normal persons is capable of producing the same 

 effect. It was found in an experiment with suckling rabbits that the 

 antitoxic property of the blood serum of M.S. was nil. It did not 

 prevent these rabbits from dying of intestinal cholera after the 

 absorption of the vibrios, in spite of a dose of three c.c. of serum 

 injected some time previously. 



This experiment, unique up to the present, is, of course, insufficient 

 to enable us to affirm that recovery from Asiatic cholera may take 

 place without the development of antitoxic power in the body fluids. 

 That this is so is, nevertheless, probable. In other intoxications of 

 microbial origin, certain data have been collected which point to the 

 same conclusion. Thus, Knorr 1 observed that the blood of guinea- 

 pigs which had recovered from tetanus did not exhibit any anti tetanic 

 power. Vincenzi 2 made a similar observation in a man who had 

 recovered from tetanus. 



We are much better informed as to the antitoxic property of the 

 blood of persons who have recovered from diphtheria. Klemensiewicz 

 and Escherich 3 have studied two cases of diphtheria in which the 

 defibrinated blood withdrawn some time after recovery was found to 

 be protective for the guinea-pig against a lethal dose of diphtheria 

 bacilli. This fact has been confirmed by several other observers, 

 especially by Abel 4 and Orlowski 5 , the latter of whom made his [465] 

 researches under the direction of Escherich. In these experi- 

 ments the antitoxic power of the blood was demonstrated against 

 diphtheria toxin employed without bacilli. According to the data 

 collected by the above authors the antitoxic property of the body 

 fluids was not exhibited during the early days of convalescence, but 

 was well marked in the second week after recovery. This power was 

 maintained for a short time only, disappearing in a few months. 

 Amongst the observations collected on this subject the most inter- 



1 Munchen. med. Wchnschr., 1898, 8. 363. 



2 Deutsche med. Wchnschr., Leipzig, 1898, S. 247. 



3 Centralbl.f. Bakteriol. u. Paratitenk., Jena, 1893, Bd. xin, S. 153. 



4 Deutsche med. Wchnschr., Leipzig, 1894, SS. 899, 936. 



5 Deutsche med. Wchnschr., Leipzig, 1895, S. 400. 



