14 THE SCOPE OF THE NEW METHOD 



been that a few persons have seen, say a beautiful 

 mitotic figure, when suddenly a later arrival at the 

 microscope says that he can see nothing, and on exam- 

 ination it has been found that the figure has completely 

 vanished owing to the onset of achromasia. If other 

 people wish to see any experiment, two or three should 

 await beside the microscope; but they may have to wait 

 a long time before a typical specimen is found, for, as 

 has been pointed out, cells rarely present exactly the 

 same appearances every time. It is of common occur- 

 rence that on one day perfect specimens continually 

 present themselves, but on the next every cell appears 

 to be distorted, or always in the wrong position. For 

 this reason we have found it better to take photomicro- 

 graphs and convert them into lantern slides rather than 

 attempt demonstrations to many people. 



It is right to mention that this method requires the 

 expenditure of patience and time on the part of the 

 investigator. One cannot attain good results in a few 

 minutes, but if some time is devoted to it the value of 

 this in-vitro method will be appreciated. 



