164 CHEMISTRY OF THE IMMUNITY REACTIONS 



forms anaphylatoxin,''" and thus causes reactions, but the whole anaphylatoxin 

 question is in so uncertain a state at the time of writing that further sf>eculation in 

 this direction is not justifiable. 



The attempts to produce antitoxin against cantharidin have not yielded con- 

 vincing results/" nor against einnephrine.^' De Angelis^* claimed that he had 

 produced specific precipitins for various natural and sj'nthetic dyes, but this work 

 has, as was to be expected, failed of confirmation.^^ Elschnig and Salus^" state 

 that melanin from the eye is antigenic, producing complement-fixing antibodies 

 specific for melanin but not for the si)ecies. Woods^' has corroborated this and 

 also demonstrated anaphylactic sensitization. We know too little concerning the 

 composition of melanin to interpret these observations. 



'^ In general terms, therefore, antigens ai'e protein molecules, and 

 the reactions of immunity are reactions against proteins foreign to 

 the body of the host, and manifested by the presence in the blood 

 of the reacting animal of substances which combine with and cause 

 recognizable changes in the foreign protein.^- These changes are 

 recognized in many ways, such as precipitation, agglutination, com- 

 plement-fixation, etc., and the question at once arises as to whether 

 these different manifestations depend each upon a separate antibody, 

 or if several or all of them are not caused by a single antibody, the 

 action of which is indicated by the different reactions which are made 

 manifest by different procedures in each case.^^ This question will be 

 discussed further in later paragraphs. 



Knowing that the antigens are merely foreign proteins which have 

 been introduced into the body of an animal, there naturalh' occurs 

 the thought that the animal body is continually receiving in its food 

 foreign proteins, and against which it defends itself in the alimentarj- 

 canal by enzymatic action, which disintegrates these proteins until 

 they have lost their colloidal character.^-* Logically following this 

 comes the idea that perhaps the reactions of immunitj' are simply 

 the same or similar disintegrative enzymatic actions, carried on within 

 the blood and tissues to protect the body in the same way against 

 foreign proteins which the alimentary digestive apparatus has not 

 had the opportunity to destroy. This conception of the nature of im- 

 mune reactions to antigens has been especially advanced and in- 



« See Manoilov, Wicn. klin. Woch., 1912 (25), 1701. 



« Champy, Compt. Rend. Soc. Biol., 1907 (G2), 1128. 



" PoUak, Zeit. physiol. Chem., 1910 (GS), C9. 



" Ann. di Ig. Spcrim., 1909 (19), 33. 



" Takemura, Zeit. Immunitiit., 1910 (5), 697. 



*" Graefe's Arch., 1911 (79), 428. 



" Jour. Immunol., 1918 (3), 75. 



^^ Drew lias found no evidence of antibody formation l\v immunizing molluscs 

 and ecliinodcrms (Jour, of Hyg., 1911 (11), 188), from which he concludes that 

 the reaction to foreign jjroteins is not a universal projierty of protoplasm; a sweep- 

 ing generalization which requires more extensive invest iagt ion for its establish- 

 ment. C'antacuzene (C'oni])t. Kend. Soc. Hiol., 1913 (74), 111) obtained precipitins 

 by immunizing J'/i(illusiii nunnilhita with mammalian l)K)i)d, l)ut no hemolysins 

 with tiiis or AjthrodUe (iculrald and Elcdone inoschata. 



"See Dean, Lancet, Jan. 13, 1917. 



" Carrel and Ingebrigsten (Jour. Exp. Med., 1912 (15). 287) have found that 

 tissues growing in vitro witli foreign blood produce iiemolytic antil>odies for that 

 blood, indicating that isolated cells can react to antigens l)v anlilxuly production. 



