xin, D, 5 Haughwout: Protozoa of Manila and Vicinity: I 183 



difficult to manage, for their vigorous movements usually carry 

 them out of range of vision before one can focus on them and 

 make out details of their structure. In such cases some colloid 

 substance that will not harm the organism may be added to 

 the medium. This has the effect of slowing their movements, 

 though their cilia or flagella will continue to vibrate. 



Among the substances that have been successfully employed 

 are solutions of cherry tree gum or quince seeds, agar-agar, or 

 carragheen. The latter substance may be obtained at any phar- 

 macy. It is a dried and bleached seaweed, which consists 

 mainly of Chondrus crispus, to which is added a small amount 

 of Gigartina mamillosa. The substance is soaked in water, until 

 it is converted into a slimy colloid mass. Small amounts may 

 be introduced under the cover glass. Carragheen may be also 

 added to the general culture, but it should be first washed in 

 a 0.5 to 1 per cent solution of sodium bicarbonate. Remove 

 the undissolved pieces at the end of a week or ten days. Change 

 the water in the culture at the end of three or four weeks. 

 Paramecium will live for months in such a medium. In the 

 absence of other material gum arable, gum tragacanth, or the 

 like may be used. A solution of 3 grams of gelatin in 100 

 cubic centimeters of water gives good results. 



On general principles morphological studies should be made 

 in a medium as closely approximating that of the natural en- 

 vironment of the animal as possible. Parasitic organisms should 

 be studied in the normal body fluid in which they occur. Use 

 physiological salt solution and similar media with caution ; they 

 may or may not be isotonic to the species under observation. 

 Failure to observe this caution may lead the worker to study and 

 describe distorted instead of normal cells. 



Motile organs, such as flagella and cilia, are often difficult to 

 see in the living cell. In such cases one may use a drop or two 

 of a strong solution of tannin or a bare trace of an alcoholic 

 solution of sulphurous acid added to a watchglassful of medium 

 containing the organisms. After the living organisms have been 

 studied, a drop of weak solution of iodine and potassium iodide 

 may be run under the cover glass, which will have the effect 

 of bringing out the cilia and flagella and, frequently, many 

 other parts. 



Weak solutions of methyl green slightly acidulated with acetic 

 acid often bring out important structures, particularly the nu- 

 cleus. The acetic acid will generally cause the discharge of the 

 trichocysts in such forms that possess them. 



