SERUM DISEASE 573 



tion goes on as usual, but the serum may not persist in the circulation. 

 Hence symptoms do not develop in such a person, although if reinjected 

 subsequently symptoms will appear. This is one reason why a con- 

 centrated serum is not so likely to produce serum sickness, since a smaller 

 quantity of it is injected. 



If, however, the patient has received an injection of serum some 

 months previously, a reinjection is likely to be followed by an immediate 

 reaction, that is, the symptoms appear within from twenty-four to forty- 

 eight hours. If the first injection had been given a year or more previ- 

 ously, no antibody may be present in the blood, so that an immediate 

 reaction does not occur. If, however, the cells once stimulated are 

 " keyed up" indefinitely, and, accordingly, antibody formation is quite 

 rapid, so that we find symptoms developing in from four to seven days 

 after injection the accelerated reaction. Or a small amount of antibody 

 may be present which gives a mild reaction around the site of serum 

 injection, followed in from four to seven days by a general reaction, 

 this being an immediate followed by the accelerated reaction. 



As was previously stated, anaphylaxis is specific that is, a person 

 receiving ox serum in the first injection would not be affected subse- 

 quently by an injection of horse serum, but only by ox serum. For this 

 reason it has been recommended that diphtheria antitoxin to be used for 

 prophylactic purposes should be prepared by immunizing cattle, re- 

 serving the horse serum for treatment if the disease should be contracted 

 subsequently. 



Symptoms of Serum Disease. The most typical of these symptoms 

 are rash, fever, and prostration, besides joint and muscle pains, edema, 

 and adenitis. 



The most obvious and important of the symptoms are undoubtedly 

 the various forms of rash. In 1000 consecutive cases of diphtheria 

 treated with antitoxin in the Philadelphia Hospital for Contagious 

 Disease, a rash developed in 430, or 43 per cent. The time of appear- 

 ance of the eruption depends, as was just stated, upon whether or not 

 the patient has been injected on a previous occasion, and if so, the 

 length of the interval between the first and subsequent injection, and 

 to a lesser extent upon the amount of the first injection, these factors 

 influencing the quantity of antibody present at the time of reinjection. 

 Of the 430 cases just mentioned, the time of appearance of the rash, in 

 days, after subcutaneous injection of antitoxin, was as follows: 



