110 INFECTION 



An essential property of a toxin lies in the fact that we can immunize 

 a subject against it, and are able to demonstrate the presence of antitoxin 

 within the serum of the immunized animal./ 



Chemical Properties of Soluble Toxins. As has just been stated, 

 the exact chemical nature of toxins is unknown. This is due principally 

 to the fact that pure toxins of bacteria are rarely obtainable, except in 

 conjunction with their associated products, such as lysins, pigments, acids, 

 etc., as well as to the great lability of the toxins. A summary of the 

 results of researches into the chemical nature of toxins would indicate 

 that they are toxalbumins, or allied to proteins. Certain investigators 

 have reported that very active toxins obtained by purification processes 

 did not give the protein reactions, yet toxins are digested by proteolytic 

 ferments, and, like proteins, are precipitated by nucleic acid (Kossel). 

 According to Field and Teague, 1 the toxins act like electropositive col- 

 loids, but diffuse faster than do proteins. Our present knowledge of 

 the chemistry of the true toxins has been expressed thus by Oppen- 

 heimer: "We must be contented to assume that they are large molecular 

 complexes, probably related to the proteins, corresponding to them in 

 certain properties, but standing even nearer to the equally mysterious 

 enzymes with whose properties they show the most extended analogies 

 both in their reactions and in their activities." 



Structure of Toxins. According to Ehrlich, the toxin molecule 

 consists of a main central atom or radical, with a large number of organic 

 side-chains grouped, as in other organic compounds, about this main 

 radical. Each of the side or lateral arms is composed of two portions 

 one, the haptophore group, which has a chemical affinity for certain 

 chemical constituents of the tissues of susceptible animals, and the other, 

 the injury-producing portion, called the toxophore group. (See Fig. 40.) 

 An animal is susceptible to a toxin only when its cells contain substances 

 that possess a chemical affinity for the haptophore group of the toxin, 

 and also substances susceptible to the toxic action of the toxophore group. 



The toxophore group is far more unstable and susceptible to dele- 

 terious influences than is the haptophore portion. When the molecule 

 has lost the toxophore radical, it is known as a toxoid, which is still 

 capable of uniting with the side arms of cells but is devoid of toxic action. 



Nature of Toxins. It has been abundantly demonstrated that 

 toxins are colloids, and in many respects bear a close resemblance to 

 enzymes. (See p. 244.) The toxins are synthetic products of bacterial 

 activity. They are of absolutely specific nature, and in this manner 



. Exper. Med., 1907, 9, 86. 





