MICRURGY 57 



measured between the temperature of that junction and the other 

 working junction gives the temperature of the second working 

 junction (above or below 0°C.) 



Owing to the great sensitiveness of electrical measuring 

 instruments, temperature can be measured to exceedingly 

 small fractions of a degree. It became Whitaker's task to 

 make a thermocouple of microscopic size. He fused wires of 

 different metals in glass or quartz (Fig. 44). By very delicate 

 technique the two wires and the quartz are brought to a micro- 

 scopic tip with the wires slightly protruding from the capillary. 

 The wires are then joined by electroplating (Fig. 44/) to form a 

 "sensitive junction." 



Experimental. — The number and variety of experiments which 

 have been performed with micrurgical instruments are many. 

 The simplest among them, such as poking an amoeba with a 

 needle point, reveals much of interest. The first thing to note 

 is whether the amoeba "minds" it. Were he a dog or even a 

 worm, he would give signs of distress if a sharp needle were 

 pushed into him, but an amoeba is a droplet of protoplasm so 

 small and relatively undifferentiated that one cannot be certain 

 that he will "mind." It is, however, sufficient to know that an 

 amoeba is protoplasm, a bit of living matter, to know that he will 

 exhibit a "nervous" response to an external stimulus. An 

 amoeba, when poked with a needle, either draws up into a ball, 

 or, if a more beUicose fellow, he will "try" his best to get away. 

 In saying that an amoeba tries, we bring up a very fundamental 

 biological and philosophical question. When man does some- 

 thing, we believe that he "knows" what he is doing. When a 

 dog does something, those of us who like dogs think that he, too, 

 knows what he is about. When a worm does something, we are 

 not quite sure that he knows; and as for an amoeba — a mere 

 microscopic drop of protoplasm — most of us are quite certain 

 that he does not know anything. But let us see if an amoeba is 

 quite as stupid as he looks. If we push a needle into him, he 

 may round up, or, as often, "run" away. This is not a mere 

 fairy tale but an experimental fact. If an amoeba is "ambling" 

 along and "hunting" for food, he will increase his speed if 

 suddenly pierced with a needle and will move in a direction away 

 from the needle (Fig. 45). The mechanist (believer in a purely 

 physical interpretation of vital phenomena) will tell us that the 



