462 SOME ZOOLOGICAL METHODS. 



Ciliata). He directs that a drop of thick aqueous solution of 

 cherry-tree gum be added to the water containing the 

 organisms (gum arabic and the like, it is stated, will not do). 

 The objects remain fixed in their places, with cilia actively 

 moving, and all vital processes retaining their full activity. 

 I am greatly obliged to Dr. GRUBLER for having been at much 

 pains in making inquiry for me, concerning the cherry-tree gum 

 that should be used. It appears that this gum is a somewhat 

 insoluble one, and it is difficult to get hold of a sample that 

 will give a good solution. Further, the solutions will not 

 keep, and must be made up fresh every day. In the face of 

 these difficulties it would seem that the method is at present 

 a far from perfect one. It should, however, be stated that 

 CEETES (Bull. Soc. Zool. France, xvi, 1891, p. 93; Journ. Roy. 

 Hie. Soc., 1891, p. 828) has found that the method gives 

 excellent results. He has also found that an intra vitam 

 stain may be obtained by adding methyl blue or " violet 

 dahlia No. 170," to the gum solution. 



A similar process of inhibiting movements whilst preserving 

 life has been worked out by JENSEN (after STAHL ; see Biol. 

 Centralb., xii, 1892, 18, 19, p. 556; Zeit. f. wiss. Mik., ix, 4, 

 1893, p. 483 ; Journ. Roy. Mic. Soc., 1892, p. 891). A solution 

 of 3 grms. of gelatin in 100 c.c. of ordinary water is made by 

 the aid of heat. This makes a jelly at the normal tempera- 

 ture. It is slightly warmed, and a drop of it is mixed in a 

 watch-glass with a drop of water containing the organisms.. 

 This plan is said to afford great facilities for the vivisection 

 of Infusoria. 



858. Staining intra vitam. The possibility of staining In- 

 fusoria intra vitam was discovered independently and almost 

 simultaneously by BRANDT (Verh. d.physiol. Ges. Berlin, 1878), 

 by CERTES (Soc. Zool., 25 janv., 1881), and by HENNEGUY (Soc. 

 philom., 12 fev., 1881). 



CERTES found that living Infusoria stain, while continuing 

 in life fora certain time, in weak solutions of cyanin, Bismarck 

 brown, dahlia, violet 5 B, chrysoidin, nigrosin, methylen blue, 

 malachite green, iodine green, and other tar colours, and hsema- 

 toxylin. The solutions should be made with the liquid that 

 constitutes the natural habitat of the organisms. They should 



