26 AIDS TO BACTERIOLOGY 



serum to the serum of a rabbit sensitised to horse serum, 

 in a test-tube. If immediately injected into a rabbit 

 anaphylactic symptoms, and perhaps death, follow. So 

 small a dose as a millionth part of a c.c. of horse serum 

 will sensitise a guinea-pig. If after a period of incubation 

 a second dose be given, the symptoms of the so-called 

 anaphylactic shock appear. Death may occur almost 

 immediately; if not, the animal becomes restless, falls over, 

 and after diarrhoea, convulsions, and respiratory failure, 

 paralysis follows. Death may occur in this state or 

 rapid recovery may follow (Theobald Smith phenomenon). 

 The hypersensitive state may be transmitted by the 

 female guinea-pig to her progeny. The blood of anaphy- 

 lactised animals, if injected into normal animals, confers 

 anaphylaxis after a large number of injections, sometimes, 

 indeed, after a single injection (passive anaphylaxis). 



No satisfactory explanation of anaphylaxis has been 

 made. Gay and Southard consider that the serum con- 

 tains a substance provisionally termed anaphylactiri, 

 which remains as a constant irritant to the cells of the 

 body, increasing their reactivity for the other constituents 

 of the foreign serum. Vaughan and Wheeler believe that 

 anaphylaxis must be due to a toxic fragment of the pro- 

 tein molecule. Richet thinks that in the injected animal 

 there is produced a substance (toxogenin) which is not 

 toxic in itself, but yields a toxic substance (apotoxin) on 

 combination with antigen. The toxicity of the apotoxin 

 (or precipitin) is increased by combination with the 

 alexin of the blood. 



In the serum the precipitin content runs parallel with 

 the severity of the symptoms, and disappears after the 

 anaphylactic condition passes off. Halliburton has 

 suggested that this explains the difference between the 

 normal and the sensitive animal. 



The frequency with which normal horse serum and anti- 

 diphtheritic serum are used in treatment, proves ana- 

 phylactic shock to be of rare occurrence among human 

 beings. Some workers question if death ever occurs, 

 outside of cases of status lymphaticus. 



Serum Disease or Serum Sickness. About one-third 

 of persons injected with horse serum for the first time are 

 found to be sensitive to it, an urticaria, more or less cedema, 

 and sometimes arthritis, appearing between the sixth and 



