DIPHTHERIA. 73 



combined with antitoxin. When more toxin is added the antitoxin 

 is dissociated from the toxon and combines with the toxin because 

 it has greater affinity for the latter substance. This continues until 

 all the antitoxin is separated from the toxon and combined with the 

 toxin, and there can be no free toxin until this point is reached. 

 Practically, however, while the diflPerence between L^ and L^ is always 

 more than 1, it is never as great as 101. Therefore, we must con- 

 clude that while there is reason for believing that there exists in 

 diphtheria cultures substances corresponding to Ehrlich's toxin and 

 toxon, the facts do not justify the statement that these bodies exist 

 in equal quantities. Moreover, as has been pointed out by Park and 

 Atkinson,* the standard for T is arbitrary and it might have been 

 placed at the amount necessary to kill a guinea-pig of 250 grams 

 within ten days, or to cause death from paralysis within two or three 

 weeks. The same critics state : " Even if the toxin molecule be 

 divided as he (Ehrlich) believes, still in any given bouillon there is 

 actual destruction, as well as production, going on all the time of all 

 substances, not only those toxic to guinea-pigs, but also of those 

 which, though non-toxic, still neutralize antitoxin." 



4. It is observed frequently that while the toxicity of a given 

 sterilized culture decreases on standing, the quantity of antitoxin 

 which it will neutralize remains constant. This observation has 

 caused Ehrlich to provide in his theory for the toxoids which have 

 already been mentioned (p. 35). 



Flexner ^ has studied quite minutely and exhaustively the patho- 

 logical lesions induced by certain bacterial toxins. Concerning the 

 gross appearances after death from subcutaneous or intraperitoneal 

 injections of sterilized cultures of the diphtheria bacillus, he makes 

 the following statement : " Much oedema, sometimes accompanied 

 with small extravasations of blood and often of an exquisite gelati- 

 nous type, was noted. The axillary and inguinal glands were 

 always, often greatly, enlarged and were congested or thickly dotted 

 with hemorrhages within the substance of the capsule and the glandu- 

 lar tissues. The corresponding lymph glands on the opposite side 

 were also enlarged, but usually less so than those on the side of the 

 inoculation. This enlargement involved the superficial and deep 

 sets. The cervical glands along the carotids and trachea to the 

 maxillae also showed an increase in size. The thyroids were without 

 exception deep brownish-red in color. The thymus gland presented 

 a rosy, and sometimes, owing to hemorrhages, a speckled appearance ; 

 the bronchial and pericardial glands, often very difficult to find in 

 the healthy animal, were quite prominent ; the mediastinal glands 

 were swollen and congested or ecchymotic. The mesenteric and 

 retroperitoneal glands were also enlarged, and sometimes considerably 



' Experimemtal Medicine, 3, 513. 



* Johns Hopkins Hospiial Be/parts, 6, 259. 



