114 INFECTION 



and leukocytes, constitutes the membranous exudate. From this focus 

 toxin is absorbed by the lymphatics and blood-stream, and distributed 

 throughout the body, the bacilli being rarely found in the blood or in- 

 ternal organs. Later the effects of toxin intoxication are shown by 

 paralyses of certain motor nerves and ganglia, particularly those of the 

 palate and heart. 



When a guinea-pig receives a subcutaneous inoculation with diph- 

 theria toxin, a typical hemorrhagic gelatinous edema develops at the 

 site of inoculation (Fig. 36). Upon opening the abdominal cavity one 

 finds but little peritoneal exudate, but the vessels of the mesentery are 

 injected and the adrenal glands show characteristic acute hyperemia (Figs. 

 37 and 38). Bloody pericardial and pleural exudates will be found in the 

 thorax, and solidified areas in the lungs. Guinea-pigs surviving a dose of 

 toxin may, after two or four weeks, begin to show paralysis of the hind 

 and then of the fore extremities, a condition analogous to the post-diph- 

 theric paralysis occurring in man and ascribed to the effects of toxon. 



Method of Testing the Virulence and Toxicity of Diphtheria Bacilli. 

 Young guinea-pigs weighing from 250 to 300 grams are quite susceptible 

 to diphtheria toxin, and are used in determining the strength of a toxin 

 and in standardizing antitoxin. The test may be of great value in the 

 management of convalescent and " carrier" cases of diphtheria, harbor- 

 ing bacilli in the upper air-passages, in determining whether the 

 microorganisms are dangerous or merely harmless non-pathogenic sapro- 

 phytes. It is practically impossible, from the morphology of the organ- 

 ism alone, to decide whether or not a given culture is dangerous, and 

 prolonged quarantine may not only be irksome and inconvenient, but, 

 if the organisms are proved to be harmless, it is unnecessary as well. 



To be reliable, however, such a test must be carried out very care- 

 fully. In the case of a highly virulent culture, the mere introduction 

 of a few organisms beneath the skin will suffice to demonstrate their 

 dangerous character, but with cultures only slightly virulent, more care 

 is necessary, for although the patient may show no ill effects as a result 

 of the presence of the bacilli, in the throat of another and less immune 

 individual they may be highly dangerous. 



The following method has been used by the author in many hundreds 

 of such tests in the Philadelphia Hospital for Contagious Diseases, and 

 has proved of distinct value: 



1. Make a culture of the part harboring the bacilli on a tube of Loffler serum 

 medium. Incubate at 35 C. for from eighteen to twenty-four hours; prepare a 

 smear and stain with Loffler's methylene-blue. If diphtheria bacilli are present, 



