THE ARTHUS PHENOMENON. 195 



sickness," carefully studied by v. Pirquet and Schick. The evidences of 

 serum sickness are numerous. Those present most frequently are fever, 

 skin eruptions, swelling of the joints, glandular enlargement and edema. 



These symptoms may follow even the very first injection of serum. They develop 

 as a rule, after an incubation period of eight to ten days; slight reddening at the 

 point of injection accompanied by moderate swelling of the regional lymph glands, 

 appear as prodromal manifestations. 



The general condition of the patient is generally only very little disturbed, in spite of 

 the frequently associated high fever. Still there are instances, especially after the intro- 

 duction of large amounts of serum, where the symptoms continue for about four to five 

 weeks and then lead to severe disturbances. 



The associated skin eruptions above mentioned, are usually of the type of an urti- 

 caria; although Hartung describes rashes simulating scarlet and measles. 



As the most positive symptoms of serum sickness, v. Pirquet and Schick 

 consider the following: 



1. The occurrence of the exanthema seven to fourteen days after injection. 



2. First appearance of the rash around the point of injection. 



3. Regional enlargement of the lymph glands. 



4. Complete absence of any changes in the mucous membranes. 



Measles is excluded by the non-presence of Koplik spots, coryza, and conjunctivitis. 

 In scarlet fever the following symptoms help to exclude serum sickness: 



1. Initial vomiting. 



2. Occurrence of angina before or at the same time as the exanthema. 



3. High fever. 



4. The simultaneous existence of the infection among others in the hospital or neigh- 

 borhood. 



If the serum disease does not arise after the first, but after a later injection, it is char- 

 acterized by the absence of, or very marked diminution in the length of the period of 

 incubation, and in addition by increased severity of the symptoms. 



Serum sickness belongs to a group of conditions designated by 

 Anaphylaxis. the terms " anaphylactic " or " hypersusceptibility " phenom- 

 ena. The subject of anaphylaxis is one of present interest 

 and its importance is manifest not only in serum sickness and in the tuber- 

 culin reaction, but in a great number of previously unexplained clinical 

 occurrences. Only few of the most important experimental observations 

 upon which this study is based, can here be reviewed. Those of Arthus 

 and Theobald Smith deserve special consideration. 



The Arthus Phenomenon. 



If a rabbit is injected subcutaneously with horse's serum at intervals of six days, a 

 soft infiltrate which remains for two to three days appears at the site of injection after the 

 fourth inoculation, a harder infiltration which continues for a longer period of time after 

 the fifth inoculation, and gangrene after the sixth or seventh. A rabbit injected sub- 

 cutaneously for a long period of time, on receiving an intravenous inoculation of horse's 

 serum, may die with severe general symptoms several minutes after the latter injection. 



