572 ANAPHYLAXIS IN RELATION TO INFECTION AND IMMUNITY 



appears to be more likely than that of others to cause these symptoms, 

 thus accounting for the fact that one lot of antitoxin will cause a higher 

 percentage of serum sickness than will another. A concentrated serum 

 is not so likely to produce serum sickness as whole serum, owing partly 

 to the fact that smaller doses of it are given. According to Rolleston and 

 Ker, the frequency of serum sickness is, as a rule, in direct proportion to 

 the amount of serum given, and in inverse ratio to the severity of the 

 attack; in other words, we may expect to encounter it most often in 

 mild and moderately severe cases that have received very liberal dosages 

 of serum. 



The Nature of Serum Disease. Serum sickness is a true anaphy- 

 lactic phenomenon. We are prone to call the severe, fatal, and rare 

 instances of death following serum injection examples of anaphylaxis, 

 and to regard serum sickness as a different condition. Both are funda- 

 mentally the same, except that in the first instance the body-cells are, 

 for some unknown reason, unduly and highly susceptible to the protein 

 poison. Fortunately, this undue hypersensitiveness is frequently fore- 

 shadowed by the asthmatic or hay-fever-like attacks which the suscep- 

 tible person may exhibit when he enters stables or is otherwise around 

 horses. It goes without saying that horse serum should never be given 

 to such persons. 



While serum sickness is usually due to horse serum, for the reason 

 that the horse is so commonly employed in the preparation of various 

 curative serums, the serum of the ox, rabbit, and other animals may in- 

 duce the same train of symptoms in addition, in some instances, to 

 producing a direct toxic effect. 



The foreign serum introduced into the human circulation acts as an 

 antigen, and calls forth the production of an antibody, the so-called 

 " ferment," which reacts with the antigen (remaining serum), causing 

 its cleavage and liberating a protein poison that acts primarily upon 

 smooth muscle and is responsible for the lesions and symptoms. An 

 immediate reaction rarely follows the first injection of serum unless the 

 patient is one of those unfortunate but rare persons who in some manner 

 have been rendered highly sensitive to horse protein. In the majority 

 of instances symptoms do not develop for from eight to twelve days, 

 during which time the antibody is being produced. When antibody 

 formation has reached a certain point, it reacts upon any of the horse 

 serum that may persist in the circulation, producing the anaphylactic 

 or protein poison. If the dose of serum has been small, antibody forma- 



