214 PHYSIOLOGY. 



The toxalbumins and venoms have other common biological 

 properties. 



ANTITOXINS. 



It is possible, 'by repeated injections of toxalbumins or venoms 

 in increasing doses,, to immunize the animal against the toxic action 

 of doses, a thousand times mortal, of the toxalbumin or venom. The 

 immune animals furnish an antitoxic serum. The toxalbumins or 

 venoms when swallowed are harmless; injected under the skin, very 

 active. Like the ferments, the toxins are destroyed by a relative 

 low temperature, about 70 C. They are precipitated by alcohol, and 

 they diaiyze with difficulty. If in a test-tube you mix the toxin and 

 the antitoxic serum in proper proportions, the mixture is harmless 

 to the animal when injected, but this countereffect requires a cer- 

 tain time for its accomplishment. These facts show that the anti- 

 toxins resemble ferments; that is, they are soluble, precipitable, and 

 diaiyze like enzymes, but are not enzymes. The basis of Ehrlich's 

 theory is that poison and counterpoison, toxin and antitoxin, directly 

 combine in any given quantity. 



The stable benzene ring and the less stable side-chains of the 

 benzene derivatives suggested to Ehrlich that living cells also con- 

 sist of a stable center and less stable side-chains. The side-chains 

 enable the cell to form chemical combinations with foodstuffs and 

 other bodies that have atom groups having a chemical affinity with 

 the atom groups in the side-chains. 



H H 



\ / \ / 



C = C C = C 



/ \ / \ 



C C H C C H 



CP P __ P 



~~ \~J \J V^ 



/ \ / \ 



II II 



Benzene nucleus or ring. Benzene. 



Ehrlich showed further that for each poison one can develop a 

 counterpoison by the process of immunizing, which has two groups 

 which are concerned in the combination with the counterpoison or 

 antitoxin. One of these, the haptophore group, is the combining 

 group proper; the other, the toxophore group, is the carrier of the 

 poison. A poison molecule might lose the one, the toxophore group, 



