304 



PLASMODROMATA AND SARCODINA 



nomenclature was reversed by Schaudinn (as Dobell has pointed 

 out) in 1903, and it is most difficult to alter it at the present time. 



History. — In 1859 Lambl published a note referring to the 

 presence of an amoeba, associated with other protozoa, in the 

 motions of a case of dysentery, and this was followed by an account 

 by Loesch in 1875 in which he states that he considers these amoebae 

 to be the cause of dysentery. Grassi, in 1879, was the first observer 

 to demonstrate the presence of amoebae in the motions of healthy 

 people, and alone or with Calandruccio described encystment, 

 while Calandruccio infected himself per os with the cysts. They 

 both noted its non-pathogenicity. Lewis and Cunningham in 1881 

 saw them in the motions of persons suffering from cholera. In 

 1894 Celli and Fiocca described and named six species of amoeba 

 occurring in man, but it is doubtful what these really are; probably 

 some of them belong to L. coli. Grassi's findings were confirmed 

 by Koch and Kartulis, but Kruse and Pasquale in a classical 

 investigation demonstrated that there were two kinds of amoebae, 

 one harmless and the other the cause of dysentery. It was not, 

 however, until Casagrandi and Barbagallo investigated and defined 

 L. coli, which is harmless, that it was possible for Jiirgens to make 

 his researches, which, extended by Schaudinn, ended in defining 

 a second amoeba named L. histolytica, ^hich. was considered to be 

 the cause of amoebic dysentery. It has been studied in detail in 

 1 91 2 by Hartmann and Whit more with important results, and in 

 an important memoir by James in 1914. 



It seems to us that Wenyon's researches into L. muris are so 

 important with regard to the opposing opinions of Schaudinn and 

 Werner on the one hand, and Hartmann and Whitmore on the 

 other, that we give this in detail. 



Loesehia muris Grassi, 1881. 



The life-history of this ama3ba has been carefully studied by Wenyon in 

 1907. L. muris lives in the caecum of mice and rats, either freely amongst 

 the contents, or upon the epithelial surface, or in the glands to their ends. 

 It measures up to 30 to 40 microns in diameter. 



The food appears to be anything at hand — bacteria, flagellates and their 

 cysts, yeast cells, and cast-off epithelial cells. 



The Trophozoite. — The narrow ectoplasm is only distinctly visible in the 

 formation of the pseudopodia, while the granular endoplasm contains the food 

 vacuoles and the nucleus, which latter is distinctly visible as a clear vesicle 

 with a distinct nucleolus. 



When stained, the nucleus is seen to have a definite fairly thick membrane, 

 with chromatinic lumps at one or two points. The nucleolus or karyosome 

 is chromatinic, and between it and the nuclear membrane is the linin network 

 with scanty granules of chromatin scattered over it. This is the type of 

 nucleus found in L. coli. 



Multiplication takes place by binary division and by encystment. In the 

 former a nuclear spindle is formed without chromosomes or an equatorial 

 plate, as the chromatin gathers at the poles, and the nucleus after elongation 

 becomes indented and then divided in the middle, and after some length of time 

 the cytoplasm divides. 



The precystic stage is distinguished by having its endoplasm cleared of all 

 large inclusions, and is surrounded by a soft gelatinous wall, through which 

 the remains of food materials can be cast out. 



