410 DIPHTHERIA 



medium be made sufficiently alkaline ; after making it neutral to litmus 

 they added to each litre of broth 7 c.c. of normal caustic soda solution. 

 There is in all oases a period at which the toxicity reaches a maximum ; 

 Eoux and Yersin found this period to be two to three weeks, but later 

 observers find that in favourable conditions the greatest toxicity is 

 reached about the tenth to twelfth day, sometimes even earlier. It 

 may be added that the power of toxin-formation varies much in 

 different races of the diphtheria bacillus, and that many may require to 

 be tested ere one suitable is obtained. 



Properties and Nature of the Toxin. — The, toxic substance in 

 filtered cultures is a relatively unstable body. When kept in 

 sealed tubes in the absence of light, it may preserve its powers 

 little altered for several months, but, on the other hand, it 

 gradually loses them when exposed to the action of light and 

 air. As will be shown later (p. 565), the toxin probably does 

 not become destroyed, but its toxophorous group suffers a sort of 

 deterioration, so that a toxoid is formed which has still the 

 power of combining with antitoxins. Heating at 58° C. for 

 two hours destroys the toxic properties in great part, but not 

 altogether. When, however, the toxin is evaporated to dryness, 

 it has much greater resistance to heat. One striking fact, 

 discovered by Ronx and Yersin, is that after an organic acid, 

 such as tartaric acid, is added to the toxin the toxic property 

 disappears, but it can be in great part restored by again 

 making the fluid alkaline. 



Guinochet found that toxin was formed by the bacilli when grown in 

 urine with no proteid bodies present. After growth had taken place he 

 could not detect protein bodies in the fluid, but, on account of the very 

 minute amount of toxin present, their absence could not be excluded. 

 Uschinsky also found that toxic bodies were produced by diphtheria 

 bacilli when grown in a protein-free medium. 1 It follows from this that 

 if the toxin is a protein, it may be formed by synthesis within the bodies 

 of the bacilli. firieger and Boer have separated from diphtheria cultures 

 a toxic body which gives no protein reaction (vide p. 192). Whether or 

 not diphtheria toxin is of proteid nature must, however, be considered to 

 be a question not yet settled, though the probability is that it is so. 



Toxic bodies have also been obtained from the tissues of those 

 who have died from diphtheria. Roux and Yersin, by using 

 a filtered watery extract from the spleen from very virulent cases 

 of diphtheria, produced in animals death after wasting and 

 paralysis, and also obtained similar results by employing the 

 urine. The subject of toxic bodies in the tissues was, however, 



1 Uschinsky's medium has the following composition : water, 1000 parts ; 

 glycerin, 30-40 ; sodium chloride, 5-7 ; calcium chloride, - 1 ; magnesium 

 sulphate, '2- "4 ; di-potassium phosphate, - 2-'25 ; ammonium lactate, 6-7 ; 

 sodium asparaginate, 3-4. 



