RESISTANCE OF THE BODY 
93 
tosis —as the protective work of these “eating” and 
“wandering cells” is called—has said that “immunity 
may be inborn or acquired.” * * The former is 
independent of the direct intervention of human art; 
the acquired immunity may come as the result of the 
spontaneous cure of an infectious disease or as the 
result of direct interference of human art, as in vac¬ 
cination and similar methods now employed by phys¬ 
icians to ward off an expected disease or to decrease 
the virulence of one already contracted.” 
This inborn immunity Newman calls “natural im¬ 
munity” and attributes it to the presence in the blood 
of soluble matters called alexines. If the alexines are 
present in sufficient quantity, the person is less or not 
at all susceptible to certain diseases, although they may 
not protect him from the attack of all disease germs. 
These alexines protect the body perfectly from all 
but the pathogenic bacteria. 
Phagocytosis seems to be a plausible theory so far 
as the germs themselves are concerned, but does not 
prove equally tenable in the case of the toxines which 
the germs have produced. Other investigators, 
notably Behring and Kitasato, do not believe that the 
phagocytes are the prime protective agency in this 
immunity. They discovered in their experiments upon 
animals that the clear, yellowish liquid part of the 
blood, or the bloom serum, taken from an animal that 
had diphtheria could and did in their test tubes destroy 
the action of the toxines of that disease. 
Natural 
Immunity 
Toxine 
