146 LEO LOEB. 



the influence of the lactose in the cells, with which the lactose 

 or component parts of the lactose comes into contact 1 



The difference between the second and third mode of action is 

 not of such a character as to render it impossible to regard the 

 latter as related to the former, especially as we do not know 

 whether intermediary processes do not also take place even in 

 those reactions, which are included under the second type. It is 

 not impossible that a similar complicated character will be shown 

 to exist in some reactions in the second class, which have been 

 regarded as direct ones. 



The presence of antibodies can, however, not always be demon- 

 strated in cases of artificially produced immunity. It has for in- 

 stance been impossible to obtain antibodies after injection of certain 

 chemical substances, which are of a less complicated character than 

 the albuminous substances mentioned above, e.g. certain alkaloids. 



If we now turn again to the adaptations, which were mentioned 

 above as occurring naturally, it is not difficult to see that a great 

 similarity exists between the natural and the experimental reac- 

 tions. The existence of an antipepsin in the mucous membrane of 

 the stomach seems analogous to the production of antiabrin in the 

 conjunctiva. In both cases we have to deal with an apparently 

 local production of an antibody. If we find in scorpions and in 

 snakes an antibody against their own venom circulating in their 

 blood, it is not unlikely that we have to deal with a reaction of the 

 second class. The fact of the leech and ankylostoma producing 

 substances inhibiting the coagulation of the kind of blood they 

 swallow may with some probability be classed among the reac- 

 tions of the third type. The same probably holds good for the 

 tissue coagulins. Whether in the case of the desert animals an 

 antibody is present does not seem to have been determined ; it is, 

 therefore, possible that we might have to deal with an acquired im- 

 munity without the presence of an antibody which can be demon- 

 strated. On the other hand it is not unlikely that further investi- 

 gation will show the existence of an antitoxin. 



Plausible as the explanation given of some of these adaptations, 

 as experiments of nature in immunity may appear, there seems 



1 The deductions of Starling and Bainbridge have recently been controverted by 

 Bierry. 



