696 SHIGELLA 



the living bacilli may become localized in the intestine and give rise to catarrhal 

 and necrotic lesions, which often prove fatal (Vaillard and Dopter 1903). 



Rabbits. — A small dose — 0-01 mgm. of a 24-hour8' agar culture of 8h. shigce — injected 

 intravenously proves fatal in 1 to 4 days. Death is preceded by diarrhoea, paresis or total 

 paralysis of the extremities, and collapse. Post mortem, there may be haemorrhages into 

 the subcutaneous tissue and peritoneum ; the intestine, especially the caecum and colon, 

 is congested and may show submucous haemorrhages. The mucosa itself is congested, 

 cedematous, and sometimes studded with petechiae (Vaillard and Dopter 1903, Amako 1908). 

 In the lumen of the gut there is often mucoid or bloody fluid. A similar picture is seen after 

 injection of dead bacilli in larger quantity, or of toxin. If a smaller dose of baciUi is given, 

 there may be time for necrosis and actual ulceration of the intestine to occur. The living 

 bacilli can be recovered from the mucosa and from the corresponding mesenteric glands. 

 Subcutaneous injection has much the same effect as intravenous, but the animals survive 

 longer. The lesions following injection of Flexner's and Sonne's bacillus are not unlike 

 those produced by 8h. shigw, if a sufficient dose is given, but they are rarely so severe. 



Mice. — 0-1 mgm. of a 24-hours' culture of Sh. shigce injected intraperitoneally or 

 Bubcutaneously kills the animal in 1 to 4 days. At necropsy there may be no evident 

 change, or there may be catarrhal inflammation of the intestine with watery mucus in the 

 gut. Sh. flexneri and Sh. sonnei often prove fatal on intraperitoneal inoculation of 

 large doses. 



Guinea-pigs. — These animals are less susceptible, weight for weight, to Sh. shigce 

 than are rabbits and mice. The lesions produced by subcutaneous or intraperitoneal 

 injection of living bacilli vary. After a fatal dose there may be no marked macroscopic 

 changes, or there may be intestinal lesions similar to those found in rabbits. Death may 

 be produced by large intraperitoneal doses of Flexner's or Sonne's bacillus. 



Other Animals.- — By giving a cat J drop of croton oil, and injecting a whole agar 

 slope of Shiga's baciUus directly into the stomach, Shiga (1898) succeeded in setting up 

 diarrhoea for a week ; the animal passed grey, shmy stools, from which the bacilli could 

 always be cultivated. It died 4 weeks later ; at necropsy there was congestion of the rectal 

 mucosa, and a covering of mucus over the whole of the large gut. The bacillus was 

 recovered from the caecum and large intestine. Most workers have failed completely to 

 reproduce true dysenteric lesions in cats, dogs, rabbits, or monkeys either by injection per 

 OS or per rectum, though the feeding of monkeys with large doses of Flexner's bacillus may 

 give rise to severe dysenteric symptoms (see Dack and Petran 1934). 



Classification. — Space does not permit of a description of the numerous attempts 

 that have been made to afford a satisfactory classification of the dysentery bacilli. 

 These may be summarized by saying that Lentz (1902) in Germany first perceived 

 the difference between the mannitol and the non-mannitol fermeiiters ; that Hiss 

 (1904) in the United States, later supported by Bojlen (1934) in Denmark, suggested 

 a classification on fermentation reactions ; that Kruse and his colleagues (1907) 

 in Germany realized the value of serological methods of classification, and had 

 the merit of pointing out the antigenic complexity of the mannitol-fermenting 

 group ; that Shiga (1908) and Amako (1908) in Japan combined fermentation 

 and serological methods ; that Gettings (1919), Murray (1918), and Andrewes 

 and Inman (1919) in England arrived independently at results agreeing closely 

 with each other, and showed that the non-mannitol-fermenting Shiga bacillus 

 was antigenically distinct and homogeneous, whereas the mannitol-fermenting 

 bacilli, of which Flexner's bacillus was the main example, were heterogeneous and 

 divisible into four types according to the preponderance of one or other of the 

 antigenic components V, W, X, and Z ; and that Boyd (1931, 1932, 1936, 1938, 

 1940) reached a different conclusion on the antigenic structure of the mannitol- 



