DIPHTHERIA 171 



becomes edematous and later necrotic. The interval between injection 

 and death is the same as after inoculation. With sublethal doses there 

 is often paralysis, beginning in the posterior extremities and extending 

 over the body. The internal organs are hyperemic with hemorrhages 

 in the adrenals, stomach and intestine. Sometimes a gastric ulcer is 

 found. It is important to note that after the first day there is a fall 

 in the blood pressure. The effects of the toxin on temperature and 

 blood pressure suggest the action of the protein poison. It will prob- 

 ably be found that the toxin is a ferment which slowly disrupts some 

 protein, setting free the poison which in small amount increases and 

 in larger, decreases the temperature and lowers blood pressure. The 

 toxin apparently has special avidity for nervous tissue. Whether this 

 action is primarily central or peripheral has not been determined. 

 When the toxin is injected into a susceptible animal it soon disappears 

 from the blood current and manifests its activity on certain organs 

 and tissues. It has not been found in the urine except when massive 

 doses are given. In insusceptible animals, it remains for a long time 

 in the blood stream and is, of course, without action on the tissues. 

 It is not able to digest the animal's proteins and it is for this reason 

 that the animal is refractory. 



We owe the discovery of diphtheria antitoxin, one of the most 

 beneficent discoveries of all ages, to the labors and genius of von 

 Behring. It is true that others had prepared the way, but this detracts 

 in no way from the debt of gratitude the world owes this distinguished 

 German investigator. To the preliminary work America made two 

 important contributions. Mitchell and Reichert showed that the active 

 principles in the venom of serpents are protein bodies or so closely 

 related to proteins that they have not been separated. Sewall immu- 

 nized pigeons to this venom. Then came the discovery by the French- 

 men, Roux and Yersin, of diphtheria toxin, closely resembling snake 

 venom in its action. Ehrlich immunized animals to the similar 

 vegetable poisons, abrin, ricin and robin, and demonstrated that passive 

 immunity could be established in other animals by the transference to 

 them of the serum of those actively immunized. Von Behring's method 

 of preparing diphtheria antitoxin as now used is as follows: Sound, 

 healthy horses are kept under observation and tested with mallein to 

 insure freedom from glanders. Injections of diphtheria toxin, begin- 



