viii. B, 4 Walker and Sellards: Entamoebic Dysentery 277 



central position occupied by the nucleus in the resting organism, 

 by the peripheral instead of central arrangement of the chro- 

 matin in the nucleus, and by the presence of 4 or 8 nuclei, instead 

 of a single nucleus, in the encysted stage; and biologically they 

 are distinguished by their parasitic instead of saprozoic mode 

 of life, by the occurrence of a reproductive process (schizogony) 

 in the encysted stage, by their inability to propagate outside of 

 the body of their host, and by not being cultivable on Musgrave 

 and Clegg's medium (compare figs. 1 and 2 with figs. 3 to 8, 

 Plate I). 



Entamoeba coli was first distinguished from another species, 

 Entamoeba histolytica, found in the intestinal tract of man by 

 Schaudinn in 1903. This species was described by "Schaudinn 

 as follows. The entamoeba shows no separation of the ectoplasm 

 from the entoplasm in the resting stage. In the motile entamoeba 

 the ectoplasm is apparent in the hyaline pseudopodes, which 

 are always less strongly refractive than the entoplasm. The 

 nucleus is vesicular, spherical in the resting entamoeba, 

 and has a thick nuclear membrane. In the center of the nucleus 

 of the vegetative entamoeba are one or more small granules 

 of plastin and chromatin. The chromatin is distributed as 

 fine granules through the achromatic network of the nucleus, 

 and appears to be collected particularly about the nuclear mem- 

 brane. Multiplication takes place in the vegetative stage by 

 simple division and by schizogony into 8 daughter entamoebse. 

 Cysts are developed, within which an autogamous sexual 

 process takes place, followed by the development of 8 nuclei 

 which give rise to 8 daughter entamoebse when the cyst is ingested 

 by a new host. 



Schaudinn (1903) found Entamoeba coli in 50 per cent of 

 healthy persons in West Prussia, in 20 per cent at Berlin, and 

 in 66 per cent of the population on the shores of the Adriatic 

 Sea. Craig (1905) found 65 per cent of 200 American soldiers 

 recruited from various parts of the United States parasitized 

 with Entamoeba coli. The occurrence of this species in the 

 United States has been confirmed by Sistrunk (1911) who found 

 it in the stools of 11 out of 145 patients suffering from diseases 

 other than dysentery at Rochester, Minnesota; by Stiles (1911) 

 who has observed it in North Carolina ; and by Rosenberger and 

 Terrell (1913) who found entamoebse in 112 out of 137 males and 

 in 81 out of 141 females examined at Philadelphia. In none 

 of these cases was there a history of diarrhoea or dysentery. 

 Vedder (1906) found Entamoeba coli in 50 per cent of healthy 



