746 



THE AMOEBAE 



rendered more conspicuous by treating with acetic acid. The nucleus stains deeply 

 with ammoniacal picro-carmine while the protoplasm is only lightly tinted. 



The amoeba is an highly mobile organism which alters its shape by the protrusion 

 and retraction of pseudopodia ; by successively altering its shape it is able to move 

 from place to place and to collect food material. A solid particle with which one 

 of the pseudopodia may have come in contact is gradually surrounded and enfolded 

 by the organism and passes into the interior of the protoplasm ; if it be suitable 



FIG. 352. Amoeba princeps. Different shapes assumed by the protozpon 

 in moving across the field of the microscope. (Duration of observation, 

 35 minutes.) 



for food it is gradually dissolved in the substance of the protoplasm, and if not 

 suitable it is soon thrown out. Intra- cellular digestion is accompanied by the 

 secretion of acid in the interior of the protoplasm (Metchnikoflf). 



Fig. 352 shows the different shapes assumed by an Amoeba princeps in the field 

 of the microscope while under observation for 35 minutes. 



Reproduction takes place in two ways : When conditions are favourable the 

 amoeba divides into two, the nucleus dividing first and the protoplasm afterwards 

 (schizogony}. 



But when the medium in which the amoeba is living begins to dry up, the protozoon 

 becomes encysted and enters upon a latent existence. During the encysted stage 

 the nucleus may divide into several secondary nuclei around which the protoplasm 

 collects, forming spores (sporogony}. When the conditions again become favourable 

 the protecting envelope is lost and the animal assumes its former characteristics. 



The Amoeba princeps can be readily cultivated in infusions of hay or straw 

 (p. 37), on similar infusions solidified with agar or on a jelly of Fuscus crispus 

 (5 per cent.), etc. 



SECTION II. THE INTESTINAL AMOEBA. 



Losch was the first to record the presence of an Amoeba in the stools of a 

 man suffering from an ulcerative affection of the intestine : this organism he 

 designated Amoeba coli. The same parasite was found in the intestines of 

 persons suffering from dysentery (Koch, Hlava) and in dysenteric abscess of 

 the liver (Nasse, Osier). Kartulis has been a strong advocate of the amoebic 



