PROTOZOA 573 



serum itself appears to act as an effective buffer. The egg-white is 

 stronger than that used by Drbohlav, being the white of four eggs to a 

 litre of Ringer's solution ; one great advantage of this stronger solution 

 is the ease with which films of the amcebae may be fixed for cytolo- 

 gical study. 



In this medium E. histolytica and E. coll usually live seven to ten 

 days, but E. gingivalis has to be transplanted into fresh tubes every 

 five or six days. 



Endolimax nana grows better in the original L.E.S. medium, since 

 this parasite does not need starch. 



Trichomonas grows very readily in the medium '' HS re + S " 

 DoBELL {Parasit., xxvi, 1934, p. 531) and Balantidinm Coli accordmg to 

 Jameson (Parasit., xix, 1927, p. 419). 



Many intestinal protozoa will grow in simpler media, and Dobell 

 (p. 538) suggests that the following might be a good double medium for 

 use in laboratories where serum is not easily obtainable, " Slopes of heat- 

 coagulated egg-white, covered with unheated egg-white diluted with 

 Ringer's fluid." 



EXAMINATION OF LIVING PROTOZOA. QUIETING OF 

 VERY ACTIVE CILIATES AND FLAGELLATES 



1121. Mechanical Methods, (a) Entangling them in the meshes 

 of cotton-wool, mycelial threads of a fungus, etc. 



(b) Increasing the viscosity of the mounting medium by adding 

 (i.) gU7n. EiSMOND (Zool. Anz., xiii, 1890, p. 723) added a drop of 

 thick aqueous solution of cherry-tree gum to the water containing 

 the organisms. Lyon (Amer. Joiirn. Physiol., xiv, 1905, p. 427) 

 found gum arable solution neutralised with caustic soda perfectly 

 successful. Certes {Journ. Roy. Micr. Sac, 1891, p. 828) added 

 an intra-vitam stain (methyl blue or violet dahlia. No. 170) to 

 the gum solution, (ii.) Gelatine. Jenson {ibid., 1892, p. 891) 

 added 1 drop of a 3 per cent, solution, warmed, to one of water 

 containing the organisms giving a concentration of 1-5 per cent. 

 (iii.) A dilute solution (about 1 per cent.) of agar may be used in 

 the same way as gelatin, and an intra-vitam stain introduced as 

 well, if desired. 



1122. Narcotisation Methods. Cocaine solutions being unstable, 

 the best results are obtained by placing a minute crystal in the 

 mounting medium under the coverslip and allowing it to diffuse 

 gradually. Myonemes can be clearly made out in this way, and 

 the working of the excretory system in Paramoecium, for example. 

 A freshly prepared 0-1 per cent, solution added in the proportion 

 of 1 to 10 of medium {i.e. making a 0-01 per cent, solution) 

 required two or three hours to prevent the stalks of \'orticellids 

 from contracting. Nearly all the peristomes had by then closed, 

 so that this method was not much good for preparing these forms 

 for fixation in the expanded form ; the same applies to other 

 narcotics tested. 



Eucain hydrochloride is stable in aqueous solution and a 1 per 



