1310 Wisconsin Academy of Sciences, Arts, and Letters. 
the custom of various laboratories to use the autoclave in this 
manner for the purpose of sterilizing blood serum, and it is very 
evident that the boiling of the serum must be absolutely pre¬ 
vented here. The following table gives the results when this 
method is used: 
Table c. 
Loss in the Closed Autoclave. 
Number of bottles 
Greatest loss. 
Smallest loss. 
Average. 
10.| 
10. 
10. 
10. 
0.4 grams 
0.4 
0.5 
0.6 
0.5 
0.1 grams 
0.1 
0.2 
0.1 
0.0 
0.26 grams 
0.26 
0.37 
0.36 
0.27 
0.30 
10. 
Total average... 
It will be seen from the above table that there is very little 
loss when the autoclave is run in this way, namely, only 0.3 of 
one per cent. 
V. The Efficiency of the Autoclave Containing Air and Steam. 
The question, then, naturally arises, does the autoclave steri¬ 
lize when run in this manner?—i. e., can it be relied upon to 
sterilize? The following experiments bear upon this point: 
The autoclave (A) was run for 20 minutes at 15 lbs. as in the 
previously described experiments, and several tubes of freshly v 
prepared and unsterilized bouillon were run with each lot of 
bottles. The bouillon tubes were then put in the incubator at 
37° C. In all cases the tubes remained sterile. Attempts were 
then made to test the efficiency of this method of sterilization 
more thoroughly as follows: Bouillon was made in the usual 
way except that it was allowed to cool down and was then in¬ 
fected with spore-bearing maternal; namely, street dust, chopped 
hay and sewage. It was then filtered through paper and run 
into bottles and autoclaved. All ten bottles remained sterile 
for many weeks. As proof of the fact that the material was 
difficult to sterilize, bottles were filled with the same bouillon 
heated in the Arnold steamer on three successive days, for from 
30 to 45 minutes and incubated. Out of twenty bottles so run, 
four developed growth. Another autoclave (B) was closed up 
cold and run for 20 minutes at 15 lbs. and failed to sterilize any 
of the twelve bottles so heated. 
