290 BACTERIOLOGY 



the blood of that animal certain solvents, or enzyme-like 

 bodies, "hemolysins," "cytolysins," etc., that react speci- 

 fically upon the blood or tissue-cells injected, agglutinating, 

 disintegrating, and finally completely dissolving them. 

 Here, too, the relations are specific. If a rabbit, for instance, 

 be rendered tolerant to or immune from beef-blood, its 

 serum dissolves only the red corpuscles of bovines; if from 

 dog's blood, then only the corpuscles of the dog are dissolved 

 by the serum of the rabbit. Similarly, if a rabbit be ren- 

 dered tolerant to injections of emulsions of epithelium cells, 

 then its serum dissolves epithelium and not necessarily 

 other cells. All these reactions may be seen in a test-tube 

 or under the microscope. 



Seventh, if a hemolyzing serum, prepared as indicated 

 under the sixth observation, be heated for a short time to 

 54°-56° C, it at once loses the hemolytic function, but 

 regains it again if a few drops of serum from a normal 

 animal be added to it. In this phenomenon of hemolysis 

 Ehrlich's "receptors of the third order" are assumed to be 

 concerned; the heating, without injuring the receptors or 

 immune bodies, destroys the "complement," and thereby 

 checks the process; but the subsequent addition of nor- 

 mal serum supplies fresh "complement," and at once 

 restores the combination necessary to the phenomenon of 

 hemolysis. 



Eighth, if blood containing a hemolysin or a cytolysin 

 be repeatedly injected into an animal, antibodies — "anti- 

 lysins"^are formed, and the serum of the animal has the 

 power of robbing a hemolytic serum of its hemolyzing func- 

 tion if mixed with it in a test-tube. 



Ninth, if normal blood, containing complement, be 

 injected into the same or another species of animal, anti- 



