MI'.l'lU DS 01"' SER0-DIAGN0SIS. '99 



remain to be proved or disproved by other workers acts also as 

 a stimulus for further research in what appears at present to be 

 an almost unlimited field. Briefly, his theory is as follows: — 

 Arguing from the structure of certain organic compounds which 

 are composed of a central stable chain or group of atoms with 

 side chains or groups which are concerned in entering into re- 

 action with atoms or groups of atoms of other elements or com- 

 pounds, he concluded that the animal cell was composed of a 

 central group of molecules, which are combined in the manner 

 most suitable for the performance of the specific functions of 

 that cell, and which entered into relations with assimilable 

 material by means of certain subsidiary side-chains of atomic 

 groupings, or, as he preferred to call these latter, receptors. These 

 receptors he regarded as being concerned normally in the per- 

 formance of the physiological nutrition of the cell, the molecules 

 of the food supplied by the body juices coming into relation with 

 the protoplasm of the cell through their agency. Now, the toxin 

 molecule he regarded as being possessed of two portions, one a 

 binding or haptophore portion, by which, he believed, the toxin, 

 when introduced into an animal's system, became bound to the 

 receptors of the cell on which the toxin acted, the poisoning effect 

 being brought about by the other group, which he termed toxo- 

 phore. If, however, the cell responded by casting off the injured 

 receptor or receptors before the central mass of protoplasm had 

 become irreparably damaged, then he thought that, in con- 

 formance with the biological law enunciated by Weigert, viz., 

 the repair of the cell being always in excess of the damage caused 

 to it, it would form a number of receptors in excess of those 

 injured by the toxin, and these being cast off from the cell, and 

 in solution in the body fluids, would constitute the antitoxin, since 

 they would bind the toxin molecules by uniting with their hapto- 

 phore groups, and thus prevent them entering into further com- 

 binations with the receptors attached to the body cells. This, 

 then, is the side-chain theory of immunity in regard to the forma- 

 tion of antitoxins, and we shall see as we proceed how it was 

 expanded in order to fit in with the facts disclosed by later 

 experiments. 



Lysins. — For a long time it was known that bactericidal and 

 haemolytic properties were present in the blood of normal animals. 

 It was in 1888 that Nuttall described the bactericidal effect of 

 normal serum on certain organisms, and, later, Buchner showed 

 that heating the serum to 55 C destroyed this lytic property. 

 Even as far back as the period between 1869 and 1875, tn e 

 existence of the normal hemolysins had been noted by Creite and 

 Landois in connection with the transfusion into animals of blood 

 of those of other species not closely related. Such transfusions 

 were noted to lead to the production of hemoglobinuria, due to 

 solution of the red corpuscles, both, it was believed, of those of 

 the treated animal and of those of the blood introduced into its 

 body. Our later and extended knowledge of these subjects may 



