406 DIPHTHERIA 



occasionally occur. The hind-limbs are usually affected first, the 

 paralysis afterwards extending to other parts, though sometimes 

 the fore-limbs and neck first show the condition. Sometimes 

 symptoms of paralysis do not appear till two or three weeks 

 after inoculation. After paralysis has appeared, a fatal result 

 usually follows in the smaller animals, but in dogs recovery may 

 take place. There is evidence that these paralytic phenomena are 

 produced by toxone, as they specially occur when there is injected 

 along with the toxin sufficient antitoxin to neutralise the more 

 rapidly acting toxin proper. This toxone is supposed by Ehrlich 

 to have a different toxic action, i.e. a different toxophorous 

 group (p. 198), from that of the ordinary toxin ; it produces 

 the late nervous phenomena, while its local action on the tissues 

 is very slight. It also has a weaker affinity for antitoxin, and 

 thus much of it may be left unneutralised. It is to be noted in 

 this connection that paralytic symptoms are of not uncommon 

 occurrence in the human subject after treatment with antitoxin, 

 the explanation of which occurrence is probably the same as 

 that just given. One point of much interest is the high degree 

 of resistance to the toxin possessed by mice and rats. Roux and 

 Yersin, for example, found that 2 c.c. of toxin, which was 

 sufficient to kill a rabbit in sixty hours, had no effect on a 

 mouse, whilst of this toxin even c.c. produced extensive 

 necrosis of the skin of the guinea-pig. 



Preparation of the Toxin. The obtaining of a very active 

 toxin in large quantities is an essential in the preparation of anti- 

 diphtheritic serum. Certain conditions favour the development 

 of a high degree of toxicity, namely, a free supply of oxygen, the 

 presence of a large proportion of peptone or albumin in the 

 medium, and the absence of substances which produce an acid 

 reaction. In the earlier work a current of sterile air was 

 made to pass over the surface of the medium, as it was found 

 that by this means the period of acid reaction was shortened and 

 the toxin formation favoured. This expedient is now considered 

 unnecessary if an alkaline medium free from glucose is used, as 

 in this no acid reaction is developed ; it is then sufficient to 

 grow the cultures in shallow flasks. The absence of glucose 

 may be attained by the method described above (p. 80), or by 

 using for the preparation of the meat extract flesh which is just 

 commencing to putrefy (Spronck). L. Martin uses a medium 

 composed of equal parts of freshly prepared peptone (by digest- 

 ing pigs' stomachs with HC1 at 35 C.), and glucose-free veal 

 bouillon. By this medium he has obtained a toxin of which 

 c.c. is the fatal dose to a guinea-pig of 500 grms. Park 



