154 



Mr. Gustav Bischof on Putrescent 



[Apr. 19, 



materials to be experimented upon, and lastly with water. Into open- 

 ing c a tin tube is fixed, which is first bent upwards and then downwards 

 in the shape of an inverted U, to prevent any Bacteria or their germs 

 from passing through this outlet-tube into the bottom of the vessel. The 

 air-pipe d, down to c, is filled with firmly compressed cotton- wool, and a 

 glass tube, sealed at its bottom, is passed down through the material experi- 

 mented upon, to allow of the temperature being measured in close 

 proximity to the meat. The vessels thus prepared are immersed in a 

 boiler filled with cold water, which is gradually heated and kept boiling 

 for several hours. The object of this is to destroy any germs adhering 

 to the meat. The temperature at the bottom of the sealed glass tube 

 was, during the boiling, in each of the following experiments 93°-95° C. 



After cooling, the Chelsea Company's water was constantly passed 

 through the vessels in the direction indicated by arrows, at as nearly as 

 possible a uniform speed. 



It is thus evident that any Bacteria of putrefaction, or their germs, in 

 the water would, after a time, render the meat putrid, or, if it remains 

 fresh, they must have been absent, or at least inactive, when the water 

 reached the meat. 

 - I now proceed to describe the experiments. 



Experiment I. — One of the vessels was filled with spongy (metallic) 

 iron, and treated as before described ; after a fortnight the meat was 

 perfectly fresh. 



Experiment II. — A vessel filled with animal charcoal; after a fortnigiit 

 the meat showed strong evidence of incipient putrefaction. As experi- 

 ments I. and II. were conducted side by side, this result proves that the 

 preservation of the meat in experiment I. was not due to any external 

 cause, such as the low temperature then prevailing. 



Experiment III. — Water continuously passed through a vessel filled 

 with spongy iron for four weeks ; even then the meat was perfectly fresh 

 and hard. 



Experiment IY. was a repetition of II., the filtration of water through 

 animal charcoal being continued for four weeks. The meat was soft and 

 quite putrid. In the course of this experiment the exit-tube was several 

 times choked by mucous matter. 



Experiment V. — In experiments I. and HI. with spongy iron, this 

 material was employed without separating any of the fine dust. In 

 order to ascertain whether Bacteria were merely mechanically retained, a 

 vessel was charged with spongy iron, from which all the finer particles 

 had been separated by a sieve with thirty holes on the linear inch. The 

 filtering medium in this case was therefore of a porous nature. After 

 four weeks' filtration the meat was perfectly fresh. 



Experiment VI.- — In the previous experiments with spongy iron the 

 meat was in contact with water, from which the iron in solution had not 

 been separated. With a view of ascertaining whether the iron in solution 



