194 APPENDIX 



neatly and without undue smearing of the vaseline. Set 

 the slides aside until the protozoa are anaesthetized by lack 

 of oxygen. The time will vary with size of drop and par- 

 ticular cultures. When finished clean all such slides and 

 covers with a strong soap or other solution. 



G. To Discharge Trichocysts of Paramecium 



Add a little fountain pen ink by touching point of the pen to 

 edge of water containing Paramecium on a slide with or 

 without cover glass. Various inks have been found effective, 

 particularly Shaeffer's "Permanent Royal Blue" and 

 Parker's "Quink." 



H. Preservation of Tapeworms 



Dogs living on the outskirts of towns or in the country where 

 rabbits abound are frequently found to be heavily infected 

 with Taenia pisiformis. Specimens of this parasite and simi- 

 lar tapeworms can be well preserved for class work in the 

 following manner. Remove the worms from the host's in- 

 testine and wash quickly in two or three changes of tap- 

 water until thoroughly clean. A large crystallization dish 

 used against a black background is a convenient receptacle. 

 Leave the worms in the clean tapwater for the few moments 

 necessary to kill them but no longer ; then lift them one by 

 one and place in another dish containing 5% formalin or 

 somewhat stronger. The worms will be well extended and 

 will not contract to any great extent if left long enough in 

 the tapwater; leaving them too long may result in macer- 

 ation. By not crowding the specimens and by seeing that 

 they are well laid out the worms can be preserved in an 

 excellent state of extension. After several days when thor- 

 oughly hardened they should be transferred to fresh 5% 

 formalin and stored without crowding in receptacles such 

 as glass fruit jars. AVorms so preserved can be examined 

 by students in the water of a dissecting pan and used many 

 times if students are cautioned against mutilation. The 

 parts of the scolex show well with a lens or under the low 

 power of a microscope; masses indicating stages in develop- 

 ment of the reproductive organs as well as the outlines of the 

 mature uterus can be recognized since formalin specimens, 

 in contrast to those preserved in alcohol, are translucent. 

 Mature proglottids can be cut into pieces and teased, as 



