114 INFECTION 



7. After death perform a careful autopsy. Make cultures of the edematous 

 area, peritoneum, and heart blood. Diphtheria bacilli may be found in the edema- 

 tous fluid, but will rarely be found in the peritoneum or in the blood. Observe whether 

 acute hyperemia of the suprarenal glands is present (Figs. 37 and 38). 



8. Not infrequently animals showing mild or even an absence of the symptoms 

 of toxemia develop paralysis of the hind quarters two or three weeks later. Accord- 

 ing to Ehrlich, this paralysis is due to the action of "toxon, " a toxic substance se- 

 creted by the bacillus or, as believed by others, a modified form of toxin. 



9. To prove that diphtheria was the cause of the toxemia or death mix 2 c.c. of 

 the culture in a test-tube with 1 c.c. of diphtheria antitoxin (500 units) . After stand- 

 ing aside for an hour at room temperature, inject the mixture subcutaneously in the 

 median abdominal line of a 250 to 300 gram guinea-pig. Symptoms of toxemia do 

 not develop. 



Standardizing Diphtheria Toxin. The strength of a diphtheria toxin 

 is estimated by injecting subcutaneously a series of guinea-pigs weighing 

 approximately 250 grams, with decreasing amounts of toxin. How 

 many dilutions will be necessary it is impossible to state; for exact results 

 several pigs of the same weight should be inoculated with the same dose, 

 and the effects should show various gradations, dependent upon the 

 size of the successive doses. In order to obtain a uniform method for 

 estimating the strength of a diphtheria toxin and thus obtain compara- 

 tive values, a standard unit has been adopted, consisting of the smallest 

 amount of toxin that mil kill a healthy guinea-pig weighing about 250 

 grams in from four to five days. This is known as the minimum lethal 

 dose, or dosis lethalis minimus. The technic used for determining this 

 dose is given in the chapter on Antitoxins, p. 232. 



A quick and accurate method for estimating the amount of diph- 

 theria toxin present in the body-fluids of a diphtheric patient would be 

 of value in controlling the antitoxin treatment of this infection. At 

 present the amount of antitoxin administered is regulated according to 

 the clinical condition of the patient. Uifenheimer has used a method 

 for determining the presence of toxin, consisting in injecting intra- 

 peritoneally a 250-gram guinea-pig with 0.1 to 0.4 c.c. of the patient's 

 serum, diluted with 2 to 4 c.c. of salt solution. The presence of a dis- 

 tinct doughy edema of the abdominal cavity after seventeen to twenty- 

 four hours indicates the presence of diphtheria toxin, an observation that 

 may be confirmed by making an autopsy at the end of forty-eight hours. 

 The diagnostic value of this method has not been adequately established : 

 it is doubtful if it yields any information other than is more readily 

 gained by making a good cultural examination of the patient, and it 

 does not aid in the estimation of the quantity of toxin, which is the result 

 most desired. 



