VIII, B, 4 Walker and Sellards: Entamoebic Dysentery 287 



Wenyon (1912) has recently conducted the most extensive and success- 

 ful experimental infections of animals with dysenteric faeces containing 

 Entamoeba histolytica yet attempted. He introduced the material con- 

 taining the entamoebaB per cesophagus and per rectum into cats. Of 14 

 experiments on 12 cats, 8 were followed by the development of acute dys- 

 entery with typical ulcerations and entamcebse in their stools, and one cat 

 developed, in addition to the dysentery, 4 abscesses of the liver. He was 

 able to pass the infection successively through 4 cats when it was lost. This 

 author was further able to study the invasion of the tissues of infected 

 cats. "The amoebae make their way to the bottom of the tubular glands in 

 the large intestine. Then they multiply and by pressure of their numbers 

 or by the exertion of their pseudopodia, and probably through some toxic 

 substance excreted by them, the lining cells are weakened and separated 

 and the amoebae pass into the connective tissue beneath." 



Craig (1913) quotes a personal communication from Creighton Welman 

 giving the data of 5 infection experiments of kittens with Entamoeba his- 

 tolytiQa performed in 1910. Two of the kittens received rectal injections 

 of faeces containing the entamoebae and 3 were fed the same material. Four 

 out of the 5 kittens developed dysenteric symptoms or showed the charac- 

 teristic lesions at necropsy. 



"Entamceba tetragena" was first described by Viereck in 1907 

 in 2 cases of dysentery from India. Shortly afterward it was 

 described under the name of "Entamoeba africana" by Hartmann 

 (1908), in cases of dysentery from Southwest Africa and South 

 America. Subsequently it has been observed by several investi- 

 gators in dysenteries in different parts of the Tropics, and it is 

 stated by Whitmore (1911) and Hartmann (1912) to be the most 

 common pathogenic species in the Philippine Islands. This ent- 

 amoeba is distinguished from Entamoeba histolytica, according 

 to Hartmann (1908 and 1912), by the nuclear structure of the 

 vegetative stage, by its reproduction, and by the structure of 

 its cysts. The nucleus of the vegetative stage, unlike that of 

 Entamoeba histohjtica, is distinctly visible in the living enta- 

 mceba, has a double-contoured membrane, and is rich in chro- 

 matin which has a characteristic arrangement. There is a 

 pheripheral layer of chromatin and a central karyosome. This 

 karyosome undergoes cyclical changes, but in its most charac- 

 teristic stage consists of a central granule, the "centriol," which 

 is surrounded by a clear halo bounded by a layer of chromatin 

 granules. "Entamoeba tetragena," unlike Entamoeba histoly- 

 tica, becomes encysted in toto and undergoes schizogony within 

 the cyst, but differs from Entamoeba coli in that only 4 merozoites 

 are formed. The unincubated cyst, therefore, contains 4 instead 

 of 8 nuclei. 



The following experimental infection of animals have been 

 attempted with entamoebse identified as "Entamoeba tetragena" : 



