58 PROTOPLASM 



needle caused a pronounced decrease in surface tension at the 

 point of entrance, leaving the anterior portion of the amoeba in 

 a state of high surface tension which caused increased movement 

 toward that end. This may be true; nevertheless, the result is 

 that the amoeba quickly moves on, away from the needle. 

 Whether we call it "intelligence," "nervous response," or 

 "tropism," the simple fact remains than an amoeba will move 

 away at an increased rate of locomotion from a disturbance which 



is causing it "discomfort." 



But our amoeba is even 

 cleverer than this. When 

 tightly held, he, on "realizing" 

 that he is inextricably caught, 

 pinches off that part of his 

 body which is held by the 

 Fig. 45. — A living Amoeba pierced by microneedle and, leaving this 



a microneedle. The Amoeba is rapidly i •, ^ i,- ir u i • j u „. ,-^JU, 



moving away from the needle which is '^^^ of hunself behmd, hurriedly 



"distressing" it. Part of the body of departs for other regions. 



the microscopic animal has already » • u au „^»„„„„„ 



disappeared from view on the right ^gam, whether We FOmaUCe 



The long protrusion of protoplasm about it OF UOt, the experi- 

 stretched by the needle will be cut off x i r a • -(-U j-U 



by the Amoeba itself close to the main cental fact IS there— the 

 part of its body and left behind. (From amoeba does the clever thing, 

 a photograph.) ^^ ^^^^^ ^^^^^ ^^^ ^^^ philoso- 



pher to decide the difference between a fox chewing off one of 

 his legs when caught in a trap and an amoeba pinching off part 

 of his body when caught by a needle. 



The reaction of an amoeba to mechanical irritation and the 

 changes (e.g., thixotropic collapse) which protoplasm undergoes 

 on dissection indicate that micrurgical operations may cause 

 very serious alterations in the behavior of an organism and in the 

 properties of protoplasm. This is true, and critics who have 

 never operated a microdissection needle like to tell about it. 

 "Your cell isn't normal! How do you know that your results 

 mean anything?" When a research worker in medicine studies 

 the action of the heart of an animal under anesthesia, he is 

 working with an abnormal organism. When exposed muscles 

 and nerves are studied, they are under abnormal conditions. 

 When animal tissues and plant seedlings are grown in culture 

 solution, the environment is abnormal. When cells are treated 

 with salts, when body fluids are withdrawn and then studied, 



