ANTIGENIC STRUCTURE 519 



more than a slight toxic effect. Dead vibrios, however, are very toxic. PfeifFer 

 (1892, 1895) found that the lethal dose of living vibrios on intraperitoneal injection into 

 guinea-pigs was 1-5 mgm. of an 18-hours' agar slope culture. When the vibrios were killed 

 by chloroform or thymol the lethal dose was 3-4-5 mgm. ; when they were killed by drying, 

 it was 6 mgm. ; and when they were killed by heat at 55° C. for an hour it was 10-20 mgm. 

 While immune serum was able to protect a guinea-pig against several fatal doses of living 

 vibrios, it possessed no more protective power than normal serum against dead vibrios. 

 From these experiments he concluded that in young cultures of V. cliolerm there was a 

 specific toxic substance bound to the bacterial bodies ; and that the immune substances 

 in the antiserum were not antitoxic but bactericidal in their action. 



Von Dungern ( 1895) working with one highly virulent strain of cholera and another of 

 very low virulence found that the lethal dose of heat-killed organisms was the same in each 

 instance. The toxicity of the cultures therefore bore no relation to their virulence. 



Manwaring, Boyd, and Okami (1923) perfused the mammalian heart with 2-7 days' 

 culture filtrates of V. cholerce, added in 5-10 per cent, concentration to Locke's solution. 

 Though non-toxic for the conducting and contractile tissues, the filtrates had a destructive 

 effect on the capillary endothelium, as was evident from the oedema of the muscle and the 

 haemorrhages that occurred beneath the endocardium and pericardium. 



We may conclude that the cholera vibrio does not secrete a true soluble exotoxin, 

 but that it contains endotoxins wMcli are liberated on the autolysis of the bacilli 

 in culture or on the active disintegration of the bacilli by the cells of the animal 

 body. The analogy that it presents with the meningococcus — another organism 

 that readily undergoes autolysis — is very close, though the cholera vibrio is far 

 more toxic. 



Hahn and Hirsch (1929), working with El Tor and other hsemolytic vibrios, found that 

 a soluble toxin was produced in peptone water cultures to which small quantities of glucose 

 were added during growth, the reaction of the medium being kept alkaline by similar 

 additions of NaOH. The toxin, which passed through a Seitz filter, became demonstrable 

 in 6-10 hours, and reached its maximum in 1-4 days. Bacterial counts indicated that the 

 increase in toxicity of the culture coincided with the death of the organisms. The heat 

 resistance of the toxin seemed to vary with different batches ; sometimes it was destroyed 

 in 2 minutes, at others not for 30 minutes, when exposed to a temperature of 100° C. In- 

 jected intraperitoneally into guinea-pigs in a dose of 0-25 ml., the toxin had a marked 

 effect on the temperature, which often fell to 30° C. within 2-3 hours. The animals became 

 progressively weaker, paralysis developed in their hind legs, and they died in 6-10 hours. 

 Post mortem, the findings consisted of a large exudate in the peritoneal cavity, fibrino- 

 purulent deposits on the liver, and sometimes hjrpersemia of the intestine. Injection of 

 horses with increasing doses of toxin led to the appearance in the serum of antibodies 

 capable of neutrahzing, to some extent, the lethal action of the toxin for guinea-pigs. 

 It is to be noted that true, non-hsemolytic, cholera vibrios were almost completely devoid 

 of toxin-producing power under the cultural conditions described (see also Andu and 

 van Niekerk 1929). Takita (1939) found that the El Tor vibrio produced a true thermo- 

 labile exotoxin neutralizable by an antiserum according to the law of multiple proportions. 

 Mice inoculated intravenously with 0-01 ml. died within 24 hours. The exotoxin appeared 

 to be different from the hsemolysin. 



Antigenic Structure. — The antigenic structure of the vibrios has of late years 

 received considerable attention. Kabeshiraa (1918), working with F. cholercB, 

 discovered the occurrence of serological variants. Balteanu (1926) found a heat- 

 labile H and a heat-stable receptor in the cholera vibrio ; immune serum prepared 

 against organisms heated to 100° C. for 2 hours contained only agglutinins. This 

 finding was confirmed and extended by Shousha (1931), Abdoosh (1932), and Gohar 

 (1932). These observations and a particularly careful study by Gardner and 



