MOVEMENTS OF IRRITATION. 



421 



possible to move the slide when necessary by means of the forceps. 

 It is still more convenient to attach the slide to a wire which 

 passes through a cork fitting into the opening F. The warm 



\f. 

 FIG. 137. Warm chamber. (After Sachs.) 



chamber is to be obtained from Leitz in Wetzlar. If it is desired 

 to work at high temperatures (we cannot go beyond 50 C., or the 

 objective will suffer), the water-jacket of the case is heated by 

 means of a spirit-lamp placed below ; when the temperature has 

 reached somewhere about the desired height, we replace the spirit- 



