552 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



individual with a certain substance had taken place; in still other cases it 

 appears to develop only gradually during the continued action of an agent 

 which has been introduced into the bodyfluids. However, in every instance 

 among a number of individuals treated apparently in the same manner, only 

 certain ones manifest such signs of hypersensitiveness ; and the persons thus 

 affected may be few or many under varying conditions. 



It has been shown especially by Cooke and Van der Veer that the tendency 

 to become sensitized against a given agent is often a hereditary characteristic, 

 in which apparently Mendelian ratios can be demonstrated. The stronger the 

 hereditary tendency is in children, the earlier the hypersensitiveness to foreign 

 protein appears. Thus, if both parents transmit to the child the tendency to 

 hypersensitiveness, the idiosyncrasy tends to appear, on the average, earlier 

 than when the transmission is unilateral. In the case of Primula extract and 

 nickel salts, Bloch has shown that while some persons can be more readily 

 sensitized than others, all persons can, in the end, be made experimentally 

 hypersensitive to these substances. But to other substances, such as iodoform, 

 salvarsan and mercury, it is much more difficult to obtain a hypersensitiveness. 

 The conclusion may then be drawn that there may exist a hereditary pre- 

 disposition which determines the readiness with which an individual can be 

 sensitized against a certain substance. 



There enter, thus, two separate factors in this set of phenomena: (1) A 

 hereditary tendency to become more or less readily sensitized by contact with 

 a certain substance; this is a factor which seems to act in a quantitatively 

 graded manner; (2) a sensitization which takes place as the result of contact 

 with a certain substance. The greater the predisposition is, the more readily 

 is the sensitization accomplished. We have here evidently to deal with condi- 

 tions similar to those which have been noted in a number of other pathological 

 conditions and especially also in cancer. In the latter condition we expressed 

 the relation between the inducing factors and the disease by the formula 

 H (Heredity) X S (Stimulation) = C (Cancer). Similarly in idiosyncrasy, 

 the relation apparently exists: H (Hereditary predisposition) X S (Sen- 

 sitization) = I (Idiosyncrasy). In malignant tumors we find all degrees of 

 hereditary predisposition to cancer, and in some cases cancer may develop 

 apparently spontaneously without long stimulation of tissues, as, especially, 

 when certin embryonal abnormalities end in cancer formation. Perhaps also 

 in cases of idiosyncrasy in which the quantity of predisposition exceeds a 

 certain limit, the quantity of external factors needed for the establishment 

 of this condition becomes so slight that these may escape recognition. There- 

 fore, in some instances the idiosyncrasy may become manifest apparently on 

 a first contact with a given substance. It is possible that we have to deal here 

 with a condition similar to that noticed in those diseases caused by micro- 

 organisms or viruses, where, in some individuals, there seem to occur spon- 

 taneously formed antibodies against the causative factor. In this latter in- 

 stance, also, the question arose as to whether or not these antibodies owed 

 their origin to the action of an antigen, which might perhaps not be identical 

 with the agent causing the disease. However, there is some evidence which 



