METHODS OF SERO-DIAGNOSIS APPLICABLE TO 

 DISEASES OF STOCK IN SOUTH AFRICA. 



By D. Kehoe, M.R.C.V.S. 



It has been thought necessary by the writer, in dealing with 

 this subject briefly to outline some of our conceptions as to the 

 manner in which the animal organism reacts to the introduction 

 of certain material either constituting or derived from other 

 organisms. 



These materials include cells, either animal or vegetable in 

 nature (bacteria), toxic products, ordinarily non-toxic albu- 

 minous substances, and ferments, and from our present point 

 of view we can apply to these bodies the collective term of 

 Antigens, since they are capable on introduction into the animal 

 body, under certain conditions, of giving rise to certain bodies, 

 which are most commonly termed Antibodies. The use of the 

 expression "antibodies" is now very widespread (although the 

 term "Reagins" has also been suggested), and we may distinguish 

 between the normal antibodies which may be found in the animal 

 in a state of nature and the acquired antibodies found in the 

 animal under either experimental or pathological conditions. 

 This division into normal and acquired antibodies is made for 

 the sake of convenience only, and does not imply that there is 

 any difference between an antibody formed under natural con- 

 ditions and an antibody with identical action which is found 

 under the conditions of experiment or disease, the difference 

 apparently being only quantitative. This naturally follows, since 

 we can only form ideas of their nature from their actions, with 

 their antigens or each other, as we are ignorant of the real nature 

 of these bodies. Their actions and inter-actions are explained 

 by some workers according to chemical theories, whilst others 

 are inclined to regard these actions as being capable of explana- 

 tion according to physical or, rather, physico-chemical laws, 

 arguing from the analogy between the behaviour of the united 

 antibody and antigen and that of colloid substances in solution 

 when influenced by the addition to that solution of either other 

 colloids or crystalloids. 



The various antibodies which we shall briefly review are the 

 Antitoxins, Antiferments, Lvsins. Agglutinins, Precipitins and 

 Opsonins, and these we shall deal with in this order, indicating 

 later how they can be made use of in sero-diagnosis. 



Antitoxins. — Between the vears t8S8 and 1S90 the discovery 

 was made by Roux and Yersin in the case of Diphtheria and 

 Faber. Brieger and Fraenkel, and Kitasato in the case of Tetanus, 

 that the organisms causing these diseases could, when grown in 

 suitable liquid media, form in the liquid certain products which, 

 on injection into the body of a susceptible animal, were capable 

 of producing symptoms similar to those caused by the living 

 bacilli causing these diseases. To the soluble germ-free products 



