20 PARASITIC AMOEBAE OF MAN. 



there occur numerous digestive vacuoles which per- 

 form the same function. In many species of amoebae, 

 especially those belonging to the genus Entamceba, 

 the exact method by which undigested food is gotten 

 rid of is still unknown, but it is probable that such 

 material is simply extruded from the periphery of 

 the organism. 



RESPONSE TO STIMULATION. Amoebae are capable 

 of responding to stimulation of either mechanical, 

 chemical, or electrical nature. 



Mechanical stimulation is best illustrated by the 

 production of pseudopodia when the organism touches 

 surfaces of any kind, and the withdrawing of the 

 pseudopodia when it is touched with a needle or when 

 it comes in contact with obstacles to locomotion. 



Response to chemical irritation is noted when a 

 solution containing some substance poisonous to the 

 organism is allowed to come in contact with it. In 

 such instances the pseudopodia are quickly with- 

 drawn and the amoeba assumes a spherical shape. 



Response to electrical stimulation is noted when 

 galvanic currents are passed through water contain- 

 ing amoebae. The organisms which are motile quickly 

 cease motion, the pseudopodia are withdrawn and a 

 spherical form is assumed. If the currents are of a 

 mild character the organisms renew their movements 

 in a variable time, but if too strong, death ensues. 



