260 On Putrescent Organic Matter in Potable Water. [Mar. 28, 



apparatus, including the remaining four tins. These being then also 

 detached, 100 cub. centims. each of filtered air were passed as before 

 into two of the tins. 



On opening the tins, which contained filtered water, the one with, 

 the other without filtered air, the meat was, after four to five weeks' 

 standing, found to be quite fresh. Nevertheless, when, after some 

 time, a drop adhering to the meat was examined under the microscope, 

 moving organisms were detected. 



The tins which contained meat and the filtered hay infusion gave 

 similar results. One pair of the tins, the one with, the other without 

 filtered air, was opened after nine weeks, and the other after nine 

 months' standing. In both cases the meat remained fresh. 



The hay infusion after filtration had a peculiar smell, reminding me 

 of some kinds of cheese. This obviously imparted to the meat a similar 

 smell, which, however, was quite distinct from that of putrid meat. 

 After the samples of meat had been standing for 24 hours, the smell 

 decreased considerably, and the following day it was hardly perceptible. 

 Between the third and sixth day the several samples exhibited gra- 

 dually the characteristic smell of putrid meat ; those samples which 

 did not contain filtered air resisting putrescence, apparently, longer 

 than the others. The filtered hay infusion, which had not been in 

 contact with meat, had, after several months' standing still, the same 

 peculiar smell. 



The conclusions which I drew in my last paper as to the antiseptic 

 properties of spongy iron upon putrefactive agents in ordinary water 

 apply therefore equally to hay infusion. However, those samples to 

 which filtered air had been supplied, prove more conclusively than my 

 experiments last year that the bacteria, or their germs, are not revived 

 when supplied with oxygen after the filtration. This, in my opinion, 

 is a result of some importance, as it demonstrates that, by filtration 

 through spongy iron, putrefaction of organic matter is not only sus- 

 pended for a time, but that it ceases entirely until reinstated by some 

 putrefactive agent foreign to the water. 



Since communicating my last paper, I have also continued the 

 inquiry, how the peculiar action, of spongy iron upon organic matter 

 is to be explained. If a rod be inserted into a body of spongy iron, 

 which has been in contact with water for some time, gas bubbles are 

 seen to escape. This gas is sometimes explosive, sometimes not. I 

 collected a quantity of the gas from two different filters, one of which 

 had been in constant operation with ordinary water for ten months. It 

 was free from any carbonic anhydride, but contained carbon and hydro- 

 gen. The hydrogen obviously results from the decomposition of water by 

 spongy iron. The carbon might be due to the decomposition of car- 

 bonaceous organic matter, or it might be produced similarly to the 

 carbo -hydrogen obtained, when dissolving ordinary iron by an acid. 



