32 COLLECTED STUDIES IN IMMUNITY. 



only one which fulfills the conditions necessary for a permanent 

 existence of a free haemolysin. 



The course of the reaction, however, is entirely different in the 

 second case, i.e., when the group a of the foreign blood-cells which 

 fits into the receptor group is found also in the organism of the 

 animal injected, being present in its blood-cells and tissues. In this 

 case, groups fitting to one another would be present in the same 

 organism. A pregnant example is seen in this, that both the rennin 

 and the antirennin group may occur simultaneously in the organism. 

 In fact we believe that this simultaneous occurrence of such corre- 

 sponding groups is a very frequent phenomenon in the economy of the 

 organism, and that it occurs especially in those cases in which a 

 certain cell is dependent for its nutrition on the products of a dif- 

 ferent kind of cell. 1 



If this is the case, i.e., when group a is present in the organism 

 beside the receptor group, the first phase will proceed just as in the 

 first case. There will be a binding, regeneration, and thrusting-off 

 of the receptor as immune body. The difference in the course of 

 the reactions becomes manifest in a second phase in which these 

 thrust-off receptors are taken up by group a. 



Under certain circumstances this might lead to serious injury, 

 namely, when the thrusting-off of the receptors as immune bodies 

 occurs so suddenly that the organism is overwhelmed, the red blood- 

 cells anchoring the receptor group and being dissolved by the ever- 

 present complement. In this case, then, an autolysin could develop. 

 But this result need not of necessity ensue. It can be prevented, 

 for example, if at first only small amounts of the liberated receptor 



1 In contrast to this we shall have to assume that singular haptophore groups 

 occur wherever it is designed to catch hold of certain exogenous constituents 

 of the nourishment. In immunization it is of some consequence whether a 

 singular group functionates as receptor, or one which corresponds to another. 

 The former is probably the case with the toxin, and this permits of an extraor- 

 dinary increase in the production of antitoxin, being limited by no regulating 

 contrivance. If, however, the antigroup is present in the organism, owing to 

 secondary influences, a regulatory production of new antigroups will occur. 

 This might be the reason why it is apparently impossible to increase the pro- 

 duction of antirennin to any desired degree. The antirennin finds the corre- 

 sponding rennin group in the organism and causes the production and thrusting 

 off of this group. As a result of this series of changes we find at one time that 

 the serum of an animal contains free antirennin, at another time that rennin 

 is being excreted by the urine. 



