300 THE MICROSCOPE. 



Algce. Ehrenberg 1 regarded and described them as Infu- 

 soria. He says : " All true Infusoria, even the smallest 

 monads, are organised animal bodies ; some consist of a 

 homogeneous jelly, and are distinctly provided with at 

 least a mouth and internal nutritive apparatus." Perceiv- 

 ing small round spots within the bodies of these animal- 

 cules, he judged them to be stomachs, in contradiction to 

 the supposition of the former great philosopher in this 

 branch of science, Miiller, in whose work, published in 

 1773, they were stated to be the animal's eggs. To test 

 the truth of his idea, and convince the world, Ehrenberg 

 fed the little things with colouring matter diffused in the 

 water which contained them. If the water be clear in 

 which the animalcule is living, the stomachs are trans- 

 parent, more so than the other parts of the body ; but are 

 rendered visible by tinting the water with pure sap green, 

 carmine, or indigo. Some of one of these colours must be 

 rubbed on a piece of glass, then a few drops of water added ; a 

 portion of the water is then allowed to run off by tilting 

 the glass on one side, and a little of the remainder of the 

 coloured matter dropped into the water containing the 

 animalcule. Portions of the coloured fluid are swallowed 

 by the animalcule, when the stomachs, from their trans- 

 parency, are distinctly seen of the same colour as the 

 liquid, while the other portions of the body remain un- 

 changed. It is now admitted that the spaces described 

 by Ehrenberg as stomachs, are vesicular, sacs either filled 

 with air or water. Sap green is the colour most easily 

 imbibed by the tiny beings; carmine shows development 

 better than any other ; whilst the indigo, which Ehrenberg 

 found to answer his purpose most satisfactorily, is rather 

 difficult to manage. Care has always to be observed that 

 the colours are not those that chemically combine with 

 water, but only such as are diffusible through the fluid in 

 a state of minute subdivision, as otherwise they are 

 poisoned by it. This important discovery of feeding the 



(1) Christian Gottfried Ehrenberg, medical councillor and professor at Berlin, 

 was born at Delitzoch in 1795, and educated at Schulpforta and Leipzig. In 

 1820-25, he, in company with Hemprich, visited Egypt and Nubia at the ex- 

 pense of the Berlin Academy; and in 1829 he accompanied Alexander von 

 Humboldt to the Ural Mountains. The results of these journeys he published 

 in various invaluable works, which will hand his name down to posterity with 

 undying honour. 



