124 Experiments on the Development of 



Capsule 4 was perfectly free from organisms, and remained so 

 during a fortnight, when a fungus-mycehum made its appearance 

 on the surface. 



Series F. Dec. 10th. — A strong infusion of turnip and cheese, 

 prepared as in Series B (sp. gr. 1013), was boiled in an eight-ounce 

 flask for five minutes. Three common test-tubes were superheated 

 and placed in a beaker to support them. 



No. 1. The infusion was poured in, and with it one drop of 

 distilled water. 



No. 2. The infusion was poured in and thus left. 



No. 3. The infusion was poured in and again boiled for two 

 minutes. 



These and the flask containing the remaining infusion were left 

 on a shelf for one day ; on Dec. 11th, there being no cloudiness in 

 any of the four, they were placed on the top of the hot-air bath. On 

 Dec. 13th No. 1 was found to be swarming with Leptothr ix-grovfths 

 and free Bacterium termo. 



No. 2 also was cloudy, and swarmed with what Cohn calls the 

 rosary-chains. No. 3 was absolutely free from all development of 

 life, and was perfectly sweet and limpid ; so also was the fluid in 

 the original flask, a large one capable of holding eight ounces. 

 How is the development of Bacteria in No. 2 to be explained ? 

 The original fluid remains pure; the fluid in No. 3, which was 

 reboiled, remains so too ; the tube itself. No. 2, had been heated 

 red-hot, and could not be a source of contamination. One's atten- 

 tion was therefore directed to the conditions of the passage of the 

 fluid from the flask into the tubes ; and here an explanation at once 

 offered itself. The large flask had not been superheated ; its lip was 

 still dirty, laden with Bacteria ready to contaminate fluids as they 

 poured from it ; hence the contamination of the fluid in test-tube 

 No. 2. The validity of this explanation cannot be disputed, be- 

 cause it is known that such glass surfaces, unless specially cleansed, 

 invariably contaminate infusions exposed to them. 



Series G. Feb. 11th. — The publication of Dr. Burden Sander- 

 son's letter, describing some experiments made by Dr. Bastian, 

 induced us to make a further series of experiments with important 

 modifications. We had expressly avoided the introduction of any- 

 thing like visible lumps of solid cheese or turnip into our infusions 

 during their ebullition, believing that such lumps were a possible 

 source of the exclusion of Bacteria or their germs from the killing 

 influence of the boiling temperature. This precaution we had sup- 

 posed (in the abisence of any statement to the opposite efiect) to 

 have been taken by Dr. Bastian in the experiments adduced by him 

 in the ' Beginnings of Life.' The presence of such lumps was 

 publicly suggested in discussion at the British Association Meeting 

 at Liverpool as a source of fallacy, and has been demonstrated to be 



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