The Anti toxins 125 



and examined in fifteen, thirty, and sixty minutes by simply looking at the dark 

 surface through the fluid. If agglutination occur, the original opalescence gives 

 place to a slightly curdy appearance, as the uniformly suspended bacteria 

 aggregate in clumps. 



If test-tubes are employed, they are best observed by tilting them and look- 

 ing through a thin layer of the contained fluid at a dark surface or at the sky. 

 In either case the flocculent collections of agglutinated bacteria can be seen. 



The test can also be made and observed under the microscope by the hanging- 

 drop method, but in working with such small quantities much of the accuracy 

 of the technic is apt to be lost. 



Some knowledge is required in order to form correct deductions from the ex- 

 periments. Thus, with typhoid bloods, the agglutination of the typhoid bacillus 

 usually occurs within an hour in dilutions of i : 50, but the agglutinability of 

 the culture employed should be known before the experiment is undertaken. 



Similarly, when the method is employed for the differentiation of bacteria the 

 agglutinative value of the serum should be known to begin with. 



The agglutinins are capable of acting as antigens and when in- 

 jected into animals effect reactions followed by the formation of 

 antibodies inhibiting their own activity. 



ANTITOXINS 



Antitoxins are immunity products by which the injurious actions 

 of toxins are annulled. In the synopsis of immunity experiments 

 already given, the history of the discovery and development of the 

 antibodies has been outlined, together with references to the 

 original contributions in which they were made public. 



In the section upon the "Explanation of Immunity" we have 

 seen that the best mode of accounting for the occurrence of antitoxins 

 is afforded by Ehrlich in the lateral-chain theory. He regards them 

 as cell haptophiles — receptors — that are formed in excess of the re- 

 quirements, by cells frequently stimulated by the presence of bacterial 

 products possessing adapted haptophores. The receptors are under 

 normal conditions engaged in maintaining the proper nutrition of 

 the cell; under abnormal conditions (as when preempted by the inert 

 or injurious haptophores of the bacterial products) are obliged to 

 increase in number to compensate for the damage done the cell. 

 Antibody formation can be induced only by antigens or bodies 

 that bear a resemblance to the normal nutrient substances absorbed 

 by the cells in that they are provided with haptophore groups 

 corresponding with the haptophile groups of the cells and so adapted 

 for union with them. Mineral and alkaloidal substances have 

 no such adaptations, but bacterial products, the toxalbumins 

 of various higher plants, venoms, enzymes, and other protein com- 

 binations have. The possession of the haptophile groups determines 

 whether or not the cell can stimulate antibody formation, and the 

 ability to produce antibodies shows the existence of the haptophore 

 groups. 



The attachment of the haptophore groups to the cells is usually 

 shown by morbid action of the cells in cases where there are as- 

 sociated toxophore and toxophile groups, as in the case of the bacterio- 



