956 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



in keeping the edge flat in the cutting-plate is entirely obviated, as the 

 downward pressure is exercised with the whole left hand, instead of 

 with the tips of the finger and thumb. 



Staining of Living Unicellular Organisms* — K. Brandt finds 

 hfematoxjlin and Bismarck-brown suitable colouring materials with 

 which to stain Protozoa in the living state. For Amoebfe and Heliozoa 

 a dilute solution of hjematoxylin in water is allowed to act for a short 

 time ; in any case the process must be limited to an hour, as even 

 Amoebae succumb to a longer treatment. Pure water should then be 

 allowed to replace the staining fluid. The nuclei are found stained 

 pale violet. By this method the author has discovered nuclein in the 

 form of niimerous round gi-anules in the endosarc of Amoebse and 

 Proteus, Leidy, measuring from ygVir to yifuff i^^- i^ diameter; they 

 have the same optical properties as the nuclei, and react chemically in 

 the same way, and stain readily and deeply with hsematoxylin. The 

 bulk of extra-nuclear nucleiu may be seen in old specimens to exceed 

 that of the nucleus itself, and in young individuals exclusively to 

 represent the nucleus. The author has been led by the remarkable 

 appearance of the so-called nuclei to regard them as reproductive 

 bodies, and to consider the nuclein granules as representing the 

 nucleus proper, for the membrane enveloping the nuclei appears in 

 this Amceha to consist of cellulose, it being insoluble in solution of 

 caustic soda, but dissolving in ammonia-oxide of copper. 



Hgematoxylin at first produces no visible change in the liquid of 

 the contractile vacuole ; this later assumes a yellowish tint, and 

 finally becomes brown shortly before death : the acid reaction of the 

 liquid is thus proved. Bismarck-brown stains the nuclei of dead 

 cells, but the only parts of Protozoa affected by it in the living state 

 are the fatty granules and a peculiar mucous substance resembling 

 cellulose. The solution should have a strength of either 1 to 3000 or 

 1 to 5000 ; it is best adapted for Heliozoa, Amoebfe, and Flagellata, 

 which remain quite healthy even after staining for several hours, and 

 when the parts above-mentioned have assumed a deep brown, if re- 

 placed in pure water ; the colour is long retained by the fat-granules. 

 Double-staining may be effected by first using Bismarck-brown 

 for an hour, and then hfematoxylin for a much shorter time ; the 

 protoplasm alone remains uncoloured. The difference in their colours 

 shows which of the granules are fatty and which consist of nuclein. 

 When death sets in, in consequence of this treatment, the nucleus be- 

 comes very deeply stained, and the protoplasm acquires some colour. 

 The action of cyanine or quinolein blue, used in the proportion of 

 1 : 100,000 or 1 : 500,000, recommended by Certes for Infusoria and 

 histological elements,! is essentially the same as that of Bismarck- 

 brown. Certes finds that Infusoria also stain with Bismarck-brown. 



Klein's Cochineal Fluid.! — Dr. E. J. Harvey recently exhibited 

 to the Dublin Microscopical Club specimens of cerebellar cortex, 



* Biolog. Centralblatt, i. (1881) pp. 202-11. 



t See ante, pp. 527 and 694. 



X Ann. and Mag. Nat. Hist, viii. (1881) p. 232. 



