1884.] 



MICKOSCOPICAL JOUKNAL. 



209 



the observation of certain gelatinous 

 substances in colored alcohol, and 

 Seiler proposed to show the grains of 

 starch in a glyceric liquid colored 

 with anilin blue. 



The coloration of the object, as 

 well as of the medium in the manner 

 ordinarily practiced, is not appli- 

 cable to living organisms. These re- 

 fuse, in fact, to absorb the coloring 

 solutions. The exceptions to this 

 rule, which Brandt and Certes have 

 indicated, are only apparent. Ac- 

 cording to Brandt, the nucleus of liv- 

 ing protozoa may be colored pale 

 violet by a dilute solution of hema- 

 toxylin, and the oily globules of these 

 creatures by Bismarck brow^n. Certes 

 has observed the latter action ^vith 

 cyanine or quinoleine blue. But in 

 all these experiments the protoplasm, 

 properly so called, remains colorless, 

 and the colored solution always ex- 

 ercises an injurious action upon the 

 vitality of the organisms ; it is only 

 tolerated in a condition of great dilu- 

 tion and during a short time. 



If, on the contrary, one applies the 

 other method, and places the living 

 things in a liquid, however slightly 

 colored, without endeavoring to color 

 the creatures themselves, death is also 

 likely to be brought on, either by ex- 

 osmosis, or more frequently by true 

 poisoning. 



It may, therefore, be useful to pos- 

 sess a strongly colored liquid which 

 is not poisonous, and which exerts 

 no sensible osmotic action upon the 

 microscopic creatures placed in it. 

 To satisfy these conditions, it suffices 

 to substitute for colored solutions 

 water holding in suspension insoluble 

 colored powders. It is from this 

 point of view that I would call atten- 

 tion to the use of Chinese ink. Its 

 innocuous nature and its intense color 

 makes it very suitable for the use of 

 which I speak. It consists, as is well 

 known, of lamp black and of gummy 

 matter, very slightly aromatized with 

 musk or camphor. By mixing it 

 v^rith v\^ater a very black liquid is ob- 

 tained, due to the fine particles of 



carbon which it holds in suspension ; 

 but this liquid does not affect living 

 cells, and organisms will live in it 

 perfectly well. 



A little China ink of good quality, 

 but not much scented, is mixed with 

 water in a porcelain dish. It is well 

 to triturate it carefully ; the liquid 

 should present, under the microscope, 

 excessively small, equal granules, 

 animated by Brownian motion ; it 

 should have, in a very thin layer, a 

 tint of a dark gray color, but not of 

 an opaque black. A drop of this 

 liquid is placed on a slide, the objects 

 to be studied are disposed on a cover- 

 glass which is applied upon the drop 

 of the black liquid. In this way the 

 black particles are prevented from 

 getting between the cover and the or- 

 ganisms to be studied. The latter 

 appear remarkably clear on the gray- 

 black ground, so that their details are 

 seen with clearness. The carbona- 

 ceous matter does not seem to incom- 

 mode the microscopic organisms ; 

 they conduct themselves very well, 

 and I have preserved the spirogyras, 

 vaucherias, and infusoria living for 

 several days. 



For prolonged observation, it is 

 naturally advisable to make use of a 

 moist chamber to prevent evaporation, 

 by placing the preparation in an at- 

 mosphere saturated with aqueous va- 

 por. Ordinarily I employ the moist 

 chamber of Strasburger, which is 

 composed of a piece of wet card- 

 board on a slide, and pierced with a 

 central circular opening upon which 

 the cover-glass is applied. The lat- 

 ter carries the organisms in a drop of 

 water on its lower surface. 



Permanent preparations may also 

 be made v^ith China ink. For this 

 purpose one replaces, little by little 

 under the cover-glass, the China ink 

 mixed in water with China ink mixed 

 in glycerin. It is always necessary 

 to so operate that the black liquid does 

 not go beyond the edges of the cover, 

 as it would produce currents by evap- 

 oration, and the black particles would 

 not be uniformly distributed. 



