280 SUMMAKY OF CUREENT RESEARCHES RELATING TO 



In default of osmic acid, filtered lemon juice may be employed ; 

 but it is necessary to follow the operation closely in order to check at 

 the right moment the action of the reagent, which should be employed 

 in a strong dose, and which consequently would in the long run injure 

 the extremely delicate tissues of the Infusoria. 



Impregnation by chloride of gold is generally successful after the 

 action of lemon juice. Often, however, the pulverulent deposit gets 

 entangled in the cilia of the Infusoria and obscures observation. Filtra- 

 tion upon glycerine reduces this inconvenience. 



In conclusion, M. Certes indicates the process which he considers 

 best for preserving the intestines of Batrachians with the object of 

 examining the parasites they enclose. Having tied the intestine at 

 the two extremities, it is washed in distilled water and placed in a 

 solution of osmic acid (1-1000). After twenty-four hours' immersion, 

 this solution is replaced by strong alcohol or by glycerinated water. 

 Under these conditions, Opalinje and other inhabitants of the 

 rectum of Batrachians may be kept undistorted till they can be 

 examined. 



In a subsequent paper,* the author mentions that he has met with 

 difficulties in the latter process. When the walls of the intestine are 

 too thick or are too much filled by food, there is so great an absorption 

 of the reagent that the Opalinae and other parasitic Infusoria are 

 dissolved under the action of the liquids of the organism or by the 

 preservative liquids. He thinks it will be found sufficient to increase 

 the strength of the osmic acid solution, and to slit the intestine 

 longitudinally. 



Staining the Nucleus of Infusoria.! — A. Certes has already 

 shown J the property possessed by cyanin or chinolin blue (and 

 Bismarck brown) of staining living tissues, the nucleus of Infusoria 

 not, however, appearing to be coloured either during life or even 

 several hours after death. Dr. Henneguy having pointed out to him 

 the analogous properties of a methyl violet, known as dahlia, M. Certes 

 has repeated his experiments with several violets, and has found that, 

 notwithstanding their very similar chemical composition, their action 

 varies considerably. Some are always toxic, and for all species of 

 Infusoria. Others only stain certain species out of those living in 

 the same liquid. Others — and this is the special object of his further 

 communication — stain the nucleus of living Infusoria, and more 

 strongly than the rest of the protoplasm. In general with the violets in 

 question, the cilia are always stained, and the liquid of the contractile 

 vacuole often participates (so far as could be judged) in the general 

 colouring. 



The phenomena of selection of the colouring matter in regard to 

 the nucleus was clearly established, at first with B B B B B violet on 

 Balantidium from the intestine of Bombinetor igneus, and then on 

 Paramecium, Vorticella, &c., with the same and dahlia violet. Gentian 



* Bull. Soc. Zool. France, vi. (1881) p. 228. 



t Ibid., pp. 226-7. 



X See this Journ;i], i. (1881) pp. 527, G94. 



