STRUCTURE AND DIVISION OF TRICHOMONAS 121 



B. MetJwds 



Aside from preparations of living flagellates in fresh eoecal 

 contents mixed with salt solution, cover-glass preparations fixed 

 and stained in various ways and mounted in balsam were em- 

 ployed. Coecal material, usually from the region adjoining the 

 mucous lining, was mixed with a little salt solution and smeared 

 out thin on clean cover-glasses. With few exceptions these 

 smears were fixed without allowing them to dry, although 

 occasionally some were dried and subsequently stained with 

 some modification of the Romanowsky method. These dried 

 smears do not give satisfactory preparations and have not been 

 used as the basis of the observations here recorded. 



For the wet smears the following fixatives, usually heated to 

 about 40°C., have been tried : Schaudinn's subhmate and alcohol, 

 with and without the addition of acetic acid; Worcester's formol- 

 sublimate-acetic ; Flemming's stronger and weaker solutions; 

 Perenyi's chrom-nitric acid; Carnoy's alcohol-chloroform-acetic; 

 Bouin's picro-f ormol-acetic ; Allen's ('16) modification of Bouin's 

 (B 15); sublimate-acetic, and picro-mereuric. The most satis- 

 factory of these have proved to be Schaudinn's, Bouin's, Allen's, 

 and Flemming's, in about the order named. Some other fixa- 

 tives were used in special experiments which will be described 

 elsewhere. 



For staining, Delafield's, Heidenhain's iron alum-haematoxylin, 

 and safranin (after Flemming's) have been tried, but most 

 of the smears have been stained with Heidenhain's haema- 

 toxylin, which has always given the most satisfactory results. 

 Alcoholic solutions of haematin, haematoxylin, and iron-alum, 

 according to the methods described by Dobell ('14) and Kofoid 

 and Swezy ('15), were tried, but did not give results as satis- 

 factory as the twenty-four-hour staining in iron alum-haema- 

 toxyhn, so their use was not continued. Various counterstains 

 were tried, but none of them appeared to add to the value of 

 the preparations, and were not generally employed. 



