112 INFECTION 



The venom of various serpents, especially that of the cobra, has 

 specific action: the erythrocytes of various animals are readily attacked 

 by it, and the cells of the respiratory center are apparently profoundly 

 affected. 



Aside from the special effects of the toxins upon certain cells and 

 tissues, it must be remembered that toxins may involve the body-cells 

 in general, and particularly those of the parenchymatous organs, such 

 as the kidneys, heart, and liver, causing coagulation of the protoplasm 

 (cloudy swelling) and final dissolution. The harm brought about by 

 the toxins or toxic products of the pyogenic group of microorganisms, 

 for instance, acts mainly in this manner. 



SPECIAL PROPERTIES OF THE PRINCIPAL TOXINS 



1. Diphtheria Toxin. Diphtheria bacilli vary considerably, both in 

 tissues and in artificial culture media, in the quantity of toxin se- 

 creted; thus in bouillon large amounts are seldom found in less than 

 from seven to fourteen days. 



The action of the toxin is dependent upon the dosage, and a certain 

 period of time must always elapse before the symptoms appear, the 

 minimum being about one day. Large doses may shorten this period 

 of incubation, but cannot diminish it below a certain limit. 



The lesion of diphtheria is practically always local, and is usually 

 situated on the mucous membrane of the upper air-passages. It is 

 characterized by the formation of a pearly white membrane that is 

 adherent to the underlying edematous tissues. The toxin produces 

 necrosis of the surface epithelium, and the product, together with fibrin 

 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 



