Allergia or Anaphylaxis 123 



these symptoms usually appearing after an incubation 

 period of eight to thirteen days, and constituting what they 

 call the "serum disease," or allergia. Sometimes these re- 

 actions are immediate; sometimes death appears imminent, 

 and, as has been observed, death sometimes occurs. 



The investigation of the subject was taken up in 1905 

 by Rosenau and Anderson*, who pursued it with great in- 

 terest and industry, by Gay,f Gay and Southard,! and 

 others. 



Experimental study shows that when an animal is injected 

 with an alien protein of almost any kind, a reaction takes 

 piace that usually is not completed under six days. If a 

 second injection is given before the reaction is perfected, the 

 mechanism of immunity is set in action, and the animal pro- 

 ceeds to defend itself through the various means described. 

 If the second administration be deferred, however, until the 

 first reaction is completed, it seems to find the animal in a 

 state of disturbed biologic equilibrium, the nature of which 

 is not understood, but which is characterized by a profound 

 disturbance that may terminate in death. The reaction is 

 quite specific; the sensitization, once effected, may continue 

 throughout the remainder of the life of the animal and be 

 transmitted from the mother to her offspring through her 

 blood. The reaction can be brought about by feeding the 

 protein or by injecting it. It has an important bearing 

 upon infection and immunity, the chief example being seen 

 in the tuberculin reaction. 



The symptomatology of anaphylaxis is interesting and 

 characteristic. When it is desirable to study it, a guinea-pig 

 is first given a sensitizing dose of horse-serum. This may 

 be very small. Rosenau and Anderson found one guinea-pig 

 to be sensitized by one-millionth of a cubic centimeter. In 

 most of their work they used less than ^1^ c.c. It is neces- 

 sary to wait until the effects of this first injection are com- 

 pletely over before giving the poisoning dose. This period 

 of incubation lasts about twelve days. After the lapse of 

 this time, the second dose, usually about y 1 ^ c.c., is given. 

 Both doses are given by injection into the peritoneal cavity. 



* "Journal of Medical Research," 1906, xv, p. 207; "Bull. No. 29 

 of the Hygienic Laboratory," Washington, D. C., 1906; "Bull. No. 

 36," 1907, Ibid.; "Jour. Med. Research," xvi, No. 3, p. 381; "Jour. 

 Infectious Diseases," iv, No. i, p. i, 1907; "Jour. Infectious Diseases," 

 vol. iv, p. 552, 1907. 



f "Jour. Med. Research," May, 1907, xvi, No. 2, p. 143. 



} Ibid., June, 1908, xvm, No. 3, p. 385. 



