ISOLATION OF A CYST 79 



through adhering firmly to the glass. The man- 

 ipulation of a single cyst in this way is most 

 laborious and uncertain, and in view of the fact 

 that there is a better method the net result is 

 simply a waste of time. The alternative method 

 we have employed is as follows : 



Take a glass capillary tube about 12 cm. long 

 and 1 mm. diameter. Flame the centre and 

 draw out quickly to the fineness of a hair. Break 

 into two equal portions, and reduce each of these 

 to a length of 6 cm., so that you have two short 

 tubes each consisting of a wider part and a very 

 fine portion. Now select a culture rich in cysts 

 and moisten with a drop of water, scraping gently, 

 so as to loosen the cysts from the jelly surface. 

 Allow a minute portion of the liquid to run into 

 the fine end of the capillary tube, and then run 

 water into the tube until about 1 cm. of the broad 

 end is filled. Mix up the contents of the tube 

 by vigorous rotation. Next prepare a small 

 2-per-cent. agar jelly film on a microscope slide, 

 and focus the upper surface with a low-power 

 objective. Tap out on to blotting-paper some 

 of the liquid in the capillary tube, and then, while 

 looking through the microscope, gently touch the 

 film with the fine end of the tube. A small 

 volume of the suspension of cysts will run on to 

 the jelly and will spread out in an area which 

 is distinctly visible, and which occupies only a 

 small portion of the field. If no cyst is present 

 or if there are more than one, place another small 

 drop on a fresh film and repeat this until you have 

 placed one cyst only on the jelly film. If the 

 suspension is too rich in cysts, dilute it until a 



