MICROSCOPY. 363 



quantities of which are sometimes transported in the air 

 (Comixes JZendus, vol. lxxxvi., p. 1552). 



Sclmlze's Mode of Intercepting the Germinal Matter of the Air. 



In 1836 Schulze described an experiment which has ob- 

 tained considerable celebrity. Placing in a flask a mixture 

 of vegetable and animal matters and water, he inserted in 

 the cork closing the flask two glass tubes, air-tight, but bent 

 at rio-ht angles above it. The infusion was boiled, and while 

 steam was issuing from the two tubes, he attached to each a 

 group of Liebig's bulbs, one filled with a solution of caustic 

 potash, the other with concentrated sulphuric acid. Apply- 

 ing his mouth on the potash side, he sucked air daily through 

 the sulphuric acid into the flask. But though the process 

 was continued from May till August, no life appeared. The 

 germs diffused in the atmosphere are supposed to have been 

 destroyed by the acid in this experiment, but others have 

 failed to obtain the same results. Professor Tyndall has re- 

 cently stated that the success of the experiment depends 

 upon passing the air-bubbles so slowly through the acid that 

 the floating matter, up to the very core of every bubble, must 

 come into contact with the surrounding liquid ; and that wa- 

 ter may be substituted for both acid and potash. His cru- 

 cial experiment was as follows : Two large test-tubes, each 

 about two-thirds filled with turnip infusion completely ster- 

 ilized, Avere so connected together that air could be drawn 

 through them in succession. Two narrow tubes passed 

 through the cork of each test-tube in the same manner as in 

 Schulze's flask ; and it was so arranged that the tube which 

 delivered the air should enter near the surface of the fluid, 

 the exit tube in each case ending immediately under the 

 cork. Two series of Liebig's bulbs, charged with pure wa- 

 ter, were attached to the two tubes of this arrangement, one 

 being connected with a large receiver of an air-pump, the 

 other left open to the air. The connection between the re- 

 ceiver and the adjacent bulb being first cut off by a pinch- 

 cock, the receiver was exhausted, and, by carefully loosening 

 the pinch-cock, a very slow passage of the air through the 

 test-tubes was secured. The rate of transfer was, however, 

 such that the air above the infusions was renewed twenty or 

 thirty times in twenty-four hours. At the end of twelve 



