198 A MANUAL OF BACTERIOLOGY 



nature. Sensitisation may be obtained, though with 

 difficulty, by administration by the mouth, and this 

 may be the explanation of the urticaria, etc., produced 

 in some individuals by certain foods, e.g. shell-fish. This 

 condition of hypersensitiveness is known as " anaphy- 

 laxis " (i.e. the opposite of " prophylaxis "). Probably 

 any antigen under appropriate conditions may induce 

 anaphylaxis, but the phenomenon has been especially 

 studied in connection with serum injections, though any 

 protein, e.g. egg-white or bacterial cells, similarly causes 

 it. The injection of an anti-serum usually produces no 

 ill-effect other than the rashes, joint pains, and pyrexia 

 already mentioned (" serum disease "), even if large 

 amounts of the serum be given extending over days or 

 even weeks, but a second injection of serum given after 

 a first injection with an interval of twelve days or more 

 between the two series of injections is liable to be followed 

 by effects which may be more or less serious, constituting 

 the so-called " anaphylactic shock." Minor disturbances 

 in the form of immediate or accelerated reactions, 

 " supersensitisation," may at other times ensue (see 

 below). 



The symptoms of anaphylactic shock are nausea and 

 vomiting, small and rapid pulse, faintness or more serious 

 heart failure, dyspnoea with rapid and shallow respiration 

 and feeling of suffocation, collapse, rigors, convulsions, 

 and even coma. The severity of the symptoms varies in 

 different Ceases, and the symptoms usually pass off in the 

 course of an hour or two ; but a few fatal cases have been 

 recorded. Death is easily produced experimentally, and 

 post mortem scattered ecchymoses are found and a dis- 

 tended condition of the lungs due to spasm and con- 

 traction of the bronchioles, to which the fatal event is due. 



The ordinary sequelae of serum injections, the rashes, 

 etc., never appear before the seventh day after the first 



