IMMUNITY, IMMUNIZATION, AND CURE. 71 



poisons (Behring's hypersensibility) ; while, on the other 

 hand, marked immunity may exist without the presence of 

 antitoxins in the blood. 



As the result of such observations, a distinction has 

 been made between tissue -immunity and serum-immunity 

 (antitoxin-immunity). The latter is a transitory condition, 

 dependent upon alterations in the blood-mixture from the 

 presence of the circulating toxins ; the first is a permanent 

 condition, dependent upon changes in the tissues, upon the 

 activity of the cells, which have become insusceptible to 

 the poisons. Tissue-immunity, or histogenic immunity, is 

 not to be referred to the presence of antitoxins. Fowl, 

 which are highly immune to tetanus, possess little if any 

 antitoxin ; but their blood becomes at once antitoxic after 

 injection of tetanus-toxin. 



Recently, Behring has returned to his original view, and 

 believes that acquired toxin-immunity, active as well as 

 passive, is always hematogenous that is, dependent upon 

 the antitoxic activity of the serum. As histogenic he con- 

 siders only the natural immunity to the bacterial poisons. 

 Finally, the antitoxins alone are as incapable as the other 

 anti-bodies or as phagocytosis of explaining all of the 

 manifestations of immunity. 



We have in the foregoing presented, as objectively as 

 possible, the facts that investigation in the domain of 

 immunity have developed in great abundance. They do 

 not permit of the establishment of a single, universally 

 applicable theoiy of immunity. They rather render it 

 probable that there is no such unity, but that immunity is 

 eventually not a simple and indivisible process, dependent 

 in all cases upon one and the same basis, but, apparently, 

 variable and complex in its nature, dependent in one in- 

 stance upon this, in another instance upon that, cause, and 

 more frequently due to several in combination. 



RELATIONS BETWEEN IMMUNITY AND CURE. In the case 

 of scarlet fever, measles, and other like diseases, recovery 

 from an attack is attended with immunity. If in the case 

 of other diseases as, for instance, pneumonia, erysipelas, 

 etc. recovery from one attack rather predisposes to subse- 

 quent attack, this does not exclude the fact that at the time 

 of recovery immunity existed, a so-called temporary im- 

 munity, which disappears in the course of a few days or 

 weeks. It is noteworthy in this connection that the dem- 



