AMCEBINA 479 



body which is connected with the thick nuclear membrane by a pro- 

 toplasmic network. 



It is not always easy to detect the nucleus in fresh or motile amoebae, 

 but under certain conditions in motionless or dead amoebae it becomes 

 evident. It may be easily shown by appropriate staining reagents. 



Biological Characters. The most striking and characteristic feature 

 of the amoeba is its motility. This may consist either in an alteration 

 of its shape or in an actual change of place. Both of these phenomena 

 are produced through the mechanism of pseudopodia. These latter 

 are rounded, blunt, and homogeneous processes formed by the more 

 or less gradual protrusion of a portion of the ectoplasm at some part 

 of the periphery of the amoeba. The motion is at times quite gradual 

 and continuous, at others sudden and jerky. The progressive move- 

 ment, that is, actual locomotion, is brought about by the protrusion of 

 pseudopodia, and into these, when they have reached a certain size, 

 the more or less granular and vacuolated entoplasm, with its contents, 

 flows with a more rapid movement than that by which the pseudo- 

 podia themselves were formed. Locomotion is generally observed to 

 take place in the direction of least resistance, a group of cellular ele- 

 ments or some detritus being sufficient to divert the course of the amoeba. 

 The amoeboid movements are also influenced by various other factors, 

 particularly by variations of temperature. They are most active at 

 the mean temperature of the human body, becoming less active as the 

 temperature falls or rises above this mean, and indeed they become quite 

 motionless in a temperature lower than 75 F. According to Boas, amoebae 

 remain alive outside of the body for not more than twenty-four hours. 



Sexual reproduction has been described by Schaudinn for some forms; 

 but the usual modes of multiplication are by simple division and by 

 division after cyst formation. Attempts to cultivate amoebae outside of 

 the body have been unsuccessful until recently, when Musgrave and 

 Clegg described the cultivation of pure species in pure cultures of 

 bacteria the " pure mixed cultures " of Frosch. 



Animal Experiments. It is evident that in the absence of artificially pro- 

 duced pure cultures of amoebae, inoculation experiments must be made 

 with material such as dysenteric stools or the contents of hepatic abscesses. 

 In a few cases where material has been obtained from hepatic abscesses 

 which have been found to contain no organisms other than amoebae, the 

 inoculations have been made in three ways: (1) by feeding animals with 

 material containing the amoebae; (2) by inoculation into the small intes- 

 tines after a preliminary laparotomy; and (3) by rectal injections with or 

 without suture of the anal orifice. The first method has always proved 

 unsuccessful, except when encysted forms were present. To the second 

 method the objection has been raised that the manipulation of the intes- 

 tines and the use of antiseptic solutions during the course of the opera- 

 tion are in themselves a source of irritation to the bowel and in some 

 cases have produced an enteritis. The third method has given, though 

 not in every case tried, positive results in the hands of Losch, Kruse, 

 Pasquale, Jurgens, and others. In the successful cases the lesions found 



