182 IMMUNITY. 



ceivable that some of these side chains combine with carbohydrates, 

 others seize upon proteids, and others still may fasten themselves to 

 molecules of fat. In this way all serve in securing nutritive material 

 for the growth, repair, or reproduction of the cell. It is also possi- 

 ble that certain pharmacological agents act upon the different tissues 

 of the body by virtue of combinations effected with these cellular 

 side chains. Now, in order for any substance to be poisonous to a 

 given animal, there must be in the body of that animal cells with 

 side chains capable of combining with the substance. A body which 

 is unable to effect a combination with any animal tissue cannot 

 be poisonous. It is not supposed that cells possess side chains 

 especially provided for the purpose of combining with poisons, but 

 it is possible that certain atomic groups which ordinarily are con- 

 cerned in securing nutritive material for the cell, may combine with 

 substances which are capable of bringing about cellular destruction. 

 On account of the close chemical resemblance between the bacterial 

 toxins and certain food principles, notably those proteid in character, 

 this supposition seems quite plausible. In the first place, then, we 

 may say that the body cells must possess toxophil side chains. By 

 this we mean that in the molecular construction of certain constit- 

 uents of the cell there are groups of atoms which may combine with 

 bacterial toxins. In the second place, a given substance, in order to 

 be toxic, must possess certain cytophil side chains. Both the toxo- 

 phil groups of the cell, and the cytophQ groups of the toxin may 

 be designated as haptophorous bodies. This means that it is by virtue 

 of these groups that the toxin enters into combination with certain 

 molecules within the cell. However, the toxin is possessed not only 

 of a haptophorous, but also of a toxophorous group, and it is by virtue 

 of the latter that injury to the cell may be accomplished. The or- 

 dinary nutritive products must, according to this theory, possess 

 cytophil haptophorous side chains, but they do not contain the tox- 

 ophorous element. Now when a small amount of a bacterial toxin is 

 introduced into the body of a susceptible animal, by virtue of its 

 haptophorous group it combines with some cell in the body. Whether 

 or not it causes a destruction of that cell depends upon the immediate 

 injury done by this combination. If the toxin be introduced in 

 sufficiently large quantity, it may completely destroy the cell, and if 

 a sufficient number of cells be destroyed, death will result. If, on 

 the other hand, the amount of toxin introduced be relatively small, 

 and the number of toxophil groups in the cell used up in the com- 

 bination be also small, the cell soon recovers from the slight injury 

 done it, but recovers deprived of the side chain which has combined 

 with the toxin. Feeling this loss and needing this side chain in 

 order to supply itself with nutritive material, the cell throws out a 

 new side chain, and when stimulated by frequent introduction of 

 small quantities of toxin, it finally not only makes good the loss with 



