78 COLLECTED STUDIES IN IMMUNITY. 



system of these cells will be occupied. On adding now an equal 

 portion of fresh blood, the latter will fail to find any free immune 

 body and cannot therefore be attacked. 



Such phenomena are exceedingly plentiful in chemistry, and it 

 may pay us to glance at some of them. IS[apthalin, as is well known, 

 consists of two benzole nuclei joined together. When, now, a salt- 

 forming group, hydroxyl or amido group, is introduced into each of 

 the two benzole nuclei, the heteronuclear substitution products, e.g., 

 dioxynaphthalin, amidonaphthol, and naphihylenediamine, or their 

 sulfo acids, will be able to combine with either one or with two mole- 

 cules of a diazo combination. When two molecules of dioxynaph- 

 thalin are mixed with two molecules of diazobenzol, the result is ex- 

 clusively the mono-azo combination; when however two molecules 

 of diazobenzol are added to one molecule of dioxynaphthalin, the result 

 is the diazo combination. If an additional molecule of dioxynaph- 

 thalin is added to the finished diazo combination, this molecule will 

 be unable to dissociate the latter, and the two substances, the diazo 

 combination and the unchanged dioxynaphthalin, will exist side by 

 side. This example, to which others, such as the esterification of 

 dibasic acids, the methylation of anilin with iodomethyl, could 

 easily be added, corresponds entirely to the relations between im- 

 mune body and erythrocytes as described by Bordet. 



It may at once be admitted that where the binding of small 

 multiples of the immune body is concerned, it is very natural to 

 think of a mechanical absorption due to the degree of concentration ; 

 and that therefore the circumstances in Bordet's case, in which the 

 binding was merely doubled, justified the comparison with staining 

 processes. The cases examined by us, however, in which at one time 

 just the solvent dose of immune body, at another an extraordinarily 

 large multiple of the dose was bound, weigh heavily against this 

 assumption. 



Our decision, however, is especially determined by certain general 

 considerations. Thus, charcoal, the type of surface-attractive agents 

 attracts thousands of substances of the most varied kind. A dye can 

 stain a large number of different substances, as is shown in every 

 stained microscopic preparation. In marked contrast to this is 

 the specificity of the numerous antibodies, which primarily are 

 always directed against the exciting bacterial or other cell 

 species. 



In the cases in which apparent deviations from this rule were 



