3i8 



PLASMODROMATA AND SARCODINA 



quite active, and takes place by short blunt or long tapering pseudo- 

 podia. The endoplasm is granular, containing non-contractile 

 food vacuoles and often red blood-corpuscles. The nucleus as a 

 rule is not distinct. 



Life-History.^ — -Reproduction apparently only takes place by 

 simple fission, while cyst formation, which has been observed, is 

 believed to be purely protective, as they contain only one nucleus. 

 The cysts may measure from 8-10 or more microns. 



Animal Experiments. — All attempts to produce dysentery in 

 animals by means of this amoeba have so far been failures. 



Pathogenicity. — -It has been accused, without sufficient proof, of 

 being the cause of pyorrhoea alveolaris. 



Doubtful Species. 



The species to be now described are not considered as ' good ' by 

 many authorities, but we give a brief account of them for the sake 

 of completeness. 



Loesehia tropicalis Lesage, 1908. 

 Lesage, from his studies of tropical dysentery, has come to the conclusion 

 that, just as there is a Loesehia coli Loesch parasitic, but non-pathogenic, in 

 the intestine of man in warm and temperate countries, so there is another 

 amoeba parasitic, but non-pathogenic, in the intestine of man in the tropics. 

 This parasite he names L. tropicalis. 



Fig. 59. — Loesehia tropicalis Lesage, 1908 .• Diagram of the Life-Cycles 



CONSTRUCTED FROM LeSAGE'S DRAWINGS. 



(Constructed from Lesage's drawings in the Bulletin de la Societe de Pathology 

 Exotique, showing binary fission and spore formation.) 



It resembles L. eoli by having a nucleus which contains much chromatin 

 and by becoming encysted, but it differs from the same in having a clearly 

 visible ectoplasm, by the small size of its cysts, and by the fact that the nucleus 

 of the cysts breaks up into a number of nuclei, which are from three to several 

 (he draws thirteen in one cyst). This entamoeba can be cultivated along with 

 bacteria, but is non-pathogenic to animals. 



Lesage considers this to be the same amoeba which was studied and culti- 

 vated by Musgrave and Clegg, and thinks that the production of dysenteric 

 symptoms in their experiments was due to contamination with the minute 

 spores of Loesehia histolytica. Walker in 1908 describes as a new species, 

 E. hominis, which may perhaps be the same as L. tropicalis. 



Pathogenicity. — It is a harmless commensal in the alimentary canal of man. 



Culture, — It can be cultivated in symbiosis with bacteria. 



