ANAPHYLAXIS 171 



The Arthus phenomenon occurs when a guinea-pig 

 receives several doses of normal horse serum at intervals 

 of some days. Another injection of horse serum then 

 causes an cedematous mass, an aseptic abscess, or an area 

 of necrosis at the site of the new inoculation, which may 

 be far removed from the region of the previous inoculations, 

 and the animal becomes cachectic and dies. 



The Theobald Smith phenomenon occurs when a guinea- 

 pig has been sensitised by a very small single dose of normal 

 horse serum, 0-01 c.c., 0-001 c.c., or even 0-000001 c.c. ; 

 if, then, after an interval of twelve to fourteen days a 

 somewhat larger dose of serum, 0-1 c.c., be given, the serious 

 symptoms of hypersensitiveness develop within a few 

 minutes, viz. respiratory failure, paralysis, clonic spasms, 

 and frequently death. At one time it was believed that 

 a small sensitising dose is more effective than a large one 

 in producing anaphylactic shock, but it has been shown 

 that this is not the case, a large dose merely lengthens the 

 incubation period (up to, it may be, forty days). The 

 reason for this may be that the toxic substance slowly 

 formed by the sensitising dose combines as it is produced 

 with a part of the antigen injected, so that the ultimate 

 result is as though a small sensitising dose had been injected. 



Various hypotheses have been advanced to account for 

 anaphylaxis. The fact that an interval or incubation 

 period is necessary for the development of the condition 

 clearly points to the formation of anti- bodies as a necessary 

 part of the phenomenon. Moreover, a " passive " anaphy- 

 lactic condition may be induced in an animal by injecting 

 it with the serum of a sensitised animal : this treated 

 animal suffers from anaphylactic shock on being injected 

 with the antigen. The substance which gives rise to the 

 anaphylactic shock is termed " anaphylatoxin " by 

 Friedberger and " apotoxin " by Richet. 



Besredka believes that anaphylaxis is caused by the 



