MICRURGY 59 



when living tissues are stained — in general, whenever chemicals 

 are added or instruments applied to organisms and cells — the 

 material is abnormal. In other words, any living object when sub- 

 jected to an experiment is in a more or less abnormal state. This is 

 experimentation, and on it does the advancement of biology depend. 

 The extent to which protoplasm will tolerate dissection is, at 

 times, slight and, at other times, very great. Pieces may be 

 repeatedly cut off from an amoeba, and the animal still lives. 



■'A» 





'^°> 



C i °o o 



^ e 





Fig. 46. — The rapid disintegration of a Fucus egg from mere puncturing with a 



needle. 



Three amputations of a goodly portion of its body, until the 

 amoeba was reduced to nearly one-fifth of its original size, left 

 it, in one experiment, in a living condition. After the fourth 

 operation, too small a remnant of its body remained to permit 

 the amoeba to survive long; it gave up in despair, coagulated, and 

 died! The amount of tolerance to injury depends, in part, on 

 the way the operation is performed. Slow movement of the 

 needles tends toward tolerance; rapid movement may cause 

 immediate disorganization. Often a cell, the egg of a seaweed 

 for example, is so sensitive to dissection that the mere prick 

 of a needle will cause an instantaneous disintegration (Fig. 46). 

 Protozoa sometimes explode in a similar manner at the slightest 

 touch. On the other hand, protoplasm will often tolerate a 



