REACTION OF THE HOST TO INFECTION 22 5 



of Buchner and Ehrlich, who fixed their attention largely upon 

 the substances dissolved in the body fluids. 



Anti-'aggressins, Specific Proteolysins. — Various substances 

 produced in the body as a result of infection show particular 

 ability td combat the effects of the soluble products of the para- 

 site to which the name aggressins has been given (see page 212). 

 Kriowledge of these substances and their behavior is still some- 

 what incomplete, but they seem to be particularly concerned 

 with the parenteral digestion of foreign proteins, a process in which 

 cytolysis may be regarded as a beginning stage. Whereas, 

 however, cytolysis is concerned with the disintegration of formed 

 material, these substances now under consideration act particu- 

 larly upon proteins already in solution. In many instances the 

 products of the first stages in this parenteral digestion are toxic 

 (disintegration of tuberculin and of egg-white), and soiiie of the 

 s)Tnptoms of infectious disease, such as fever, have been ascribed 

 to them. In their general characters these lytic substances are 

 wholly analogous to the cytolysins and their action is due to at 

 least two components, an amboceptor and a complement. 



Source and Distribution of Atitibodies.^ — The exact source' 

 of the antibodies dissolved in the body fluids is unknown. All 

 agree that they are derived from cells. Metchnikoff regards 

 the phagocytic cells as the important source; Ehrlich does not 

 specify, but it would seem, in accordance with his theory, that 

 any cell capable of being affected by the foreign substance should 

 be capable of throwiisg off cell receptors (antibodies) to combine 

 with it. Many investigators consider antibody formation to be a 

 common property of maliy kinds of cells, but more especially of rela- 

 tively undifferentiated cells such as those of the connective tissue. '■ 



Antibodies are present in greatest concentration in the blood 

 and lymph. They are absent or present only in small amount 

 in the serous fluids of the pleural, pericardial, peritoneal and 

 joint cavities, and in the cerebrospinal fluid. ^ Parasites in 



' See Flexner, Harbin Lectures, Journ. of the State Medicine, March, April, May 

 1912. 



15 



