PROPERTIES OF THE TOXIN 261 



inoculation ; this is soon followed by panting respiration and death super- 

 venes in 20-30 hours. 1 



Post mortem the lesions found are similar to those described as following 

 the inoculation of living bacilli. 



Smaller doses (0'005-0'002 c.c.) of a powerful toxin kill guinea-pigs after 

 the lapse of 5-30 days, but if the dose be too small the animal will survive. 

 Paralysis is very rarely seen in guinea-pigs. 



On the rabbit. The administration of 0'25-0'5 c.c. toxin either sub-cutane- 

 ously or into a vein terminates in death accompanied by the usual lesions. 

 If the dose be not large enough to kill the animal very rapidly typical diph- 

 theria paralyses develop. 



If toxin be applied to mucous membranes, local lesions and occasionally 

 true false membranes form even though the surface be intact (Roger and 

 Bayeux, Morax and Elmassian). 



On the dog. Dogs are very susceptible to the action of diphtheria toxin. 

 A dose of 1 c.c. sub-cutaneously is sufficient to kill a dog rapidly with symptoms 

 of jaundice and diarrhoea ; lesions will be found in the liver post mortem. 

 Smaller doses are followed by paralyses : the animal may recover but if 

 death takes place it does not occur so rapidly as when larger doses are 

 used. 



On birds. Fowls, pigeons and small birds rapidly succumb to very small 

 doses of toxin whether the inoculation be made beneath the skin or into the 

 pectoral muscle. 



Ruminants. Goats are very susceptible to diphtheria toxin ; similarly, 

 cows often succumb to the inoculation of a fraction of a c.c. of toxin. Sheep 

 are somewhat less susceptible, 



Horses. The horse is less affected by diphtheria toxin than ruminants ; 

 but a dose of O'l c.c. of a toxin of which the lethal dose for guinea-pigs 

 was 75-iy c.c. has been known to kill a horse weighing 400 kg. The ass is 

 more susceptible. 



Rats and mice are nearly immune to the action of toxin when inoculated 

 sub-cutaneously : the dose of toxin required to kill a mouse would kill as 

 many as 24 to 100 guinea-pigs (Roux and Yersin). 



On the other hand intra-cerebral inoculation of O'l c.c. of toxin kills rats 

 with symptoms of diphtheria paralysis (Roux and Borrel). 



The brain of the rat is therefore sensitive to the action of diphtheria toxin, and 

 the reason why the animal does not die as the result of sub-cutaneous inoculation 

 of large quantities of the poison is because the latter is fixed by certain cells in the 

 tissues (probably by the phagocytes), and so never reaches the cerebrum. 



(d) On the nature and properties of diphtheria toxin. 



The problem of the nature of diphtheria toxin has been the subject of 

 prolonged and extensive investigations. Brieger and Frsenkel as well as 

 Wassermann and Proskauer regarded toxin as a tox-albumin, and Gamaleia 

 considered it to be a nucleo-albumin : but these observers only succeeded in 

 obtaining very impure products containing relatively very little toxin. Roux 

 and Yersin have shown that the active principle in filtered cultures has the 

 chief properties of enzymes. A temperature of 100 C. destroys diphtheria 

 toxin : an exposure to a temperature of 58 C. for 12 hours lowers its toxicity 

 to such an extent that 1 c.c. of the heated toxin fails to kill a guinea-pig ; 

 and the effect of heating to 70 C. is to attenuate the toxin even more. In 

 common with the diastases, diphtheria toxin has the property of being carried 



[ x Sub-cutaneous inoculation is always followed by an incubation period before symptoms 

 appear.] 



