STAINING LIYING BODIES. 253 



normal state. Infusoria thus coloured were kept for 

 nearly fifteen days. If a yellow-tinted Paramoecium is 

 wounded or compressed so as to cause a small quantity 

 of the protoplasm to exude, it is seen that it is really 

 the protoplasmic substance which is coloured. All 

 Infusoria may be equally stained with Bismarck 

 brown, but no other aniline colours employed exhibit 

 the same property they only stain the Infusoria after 

 death, and some of them are in fact poisonous. As it 

 is generally admitted that living protoplasm does not 

 absorb colouring matters, and that Infusoria are essen- 

 tially composed of protoplasm, an attempt has been 

 made to ascertain whether protoplasm in general, of 

 animal or vegetable origin, behaved in the same way 

 in the presence of aniline brown. A tolerably strong- 

 dose of Bismarck brown was injected under the skin of 

 the back of several frogs. After some hours the tissues 

 were uniformly tinted a deep yellow; the muscular 

 substance especially had a very marked yellow tint. 

 The frogs did not appear in the least incommoded. 

 Small fry of trout placed in a solution stained rapidly 

 and continued to swim about. Finally, a guinea-pig, 

 under whose skin some powder of Bismarck brown had 

 been introduced, soon presented a yellow staining of 

 the buccal and anal mucous membranes and of the skin. 

 Seeds of cress sown on cotton soaked with a concen- 

 trated solution of the Bismarck brown sprouted, and 

 the young plants were strongly stained brown; but on 

 crushing the tissues and examining them under the 

 microscope, it was ascertained that the protoplasm of 

 the cells was very feebly coloured ; the vessels, on the 

 contrary, showed a very deep brown staining up to 

 their termination in the leaves. The mycelium of a 

 mould which had been developed in a solution of 

 Bismarck brown, was clearly stained after having been 

 washed in water, whilst it is known that the mycelium, 

 which frequently forms in coloured solutions, picro- 

 carmine, haematoxylin, &c., remains perfectly colour- 

 less. Other aniline colours injected under the skin of 

 frogs stained the fundamental substance of the con- 

 nective tissue as deeply as did the Bismarck brown ; 



