18 PEACTICAL PABASITOLOGY 



a small portion of the medium containing the organisms being cut out, 

 fixed whole, and finished in the usual manner. 



(b) Parasitic Amcebce. 



Among the Amoebae parasitic in man, two varieties are entirely 

 innocuous. They are of wide distribution and, where there is access 

 to hospital material, readily obtainable. 



(1) Entamceba buccalis, Prow., is found in the mouth, in the 

 deposit upon the teeth under the gums, and especially in carious 

 teeth. It occurs in most human beings, though generally in small 

 numbers only. It is distinguished from the leucocytes by its larger 

 size (6 to 32 /JL), its higher refractive index, and the nature of its move- 

 ments. The latter are performed by means of broad pseudopodia 

 which are pushed out like a hernial sac. The living E. buccalis, 

 moreover, when stained with neutral red, takes on a deeper colour 

 than the leucocytes. There is marked differentiation between the 



FIG. 1. Entamceba buccalis. a d, The same individual in four stages of movement, 

 during an observation period of five minutes . (magnified about 1,000 : 1) ; e, a fixed 

 specimen coloured with iron-hsematoxylin (magnified about 1,500 : 1). (From Braun, 

 after Leyden and Lowenthal.) 



hyaline ectoplasm and the nucleated endoplasm, the latter frequently 

 containing numerous food boluses (fragments of leucocytes, bacteria, 

 &c.). In the living organism, the nucleus, with its thick nuclear 

 membrane and distinct caryosome, is frequently obscured by these 

 food boluses. It is seldom possible to watch the process of repro- 

 duction (by simple fission), and the stages preparatory to encysting 

 are even more difficult of observation. 



E. coli (Losch), Schaud., is found in most healthy people in the 

 first part of the large intestine. Its numbers vary in individuals 

 and localities, and it is apparently more numerous in the country 

 than in the town. Its presence is demonstrated by the occurrence of 

 characteristic round, eight-nucleated cysts in the faeces. During diar- 

 rhoea, which may be artificially induced, resting-cells and young cysts 

 are passed. The movements of this Amoeba can only be studied by 



