26 
C. A. LUDWIG 
pigment was usually nearly or quite lacking and the development 
very slight. It will be noted that if we take B. Kieliensis as a test 
organism carbon monoxide appears to be just about as toxic as illumi- 
nating gas. 
Bacillus ruhidus. — In the case of B. ruhidus a single successful 
series of cultures with carbon monoxide showed a retardation in the 
rate of development at lo percent; at 25 percent it was quite marked; 
at 50 percent and 75 percent the development was very slight at the 
end of a 5-day period; and at 100 percent (uncorrected) there was no 
visible development. After return to the air vigorous growth took 
place in 2 to 3 days. This organism was not included in the supple- 
mentary test with the gas that was stored in the mercury seal 
gasometer. 
Sarcina lutea. — The development of S. lutea was normal or nearly 
so to 10 percent of the gas but at 25 percent the inhibitive effect 
was clearly noticeable. At 50 percent to 75 percent the development 
was very slight during an 8-day period of exposure. At 100 percent 
(uncorrected) there was very little if any discernible growth. 
Oidiiim lactis. — Carbon monoxide exerted a definite checking effect 
on 0. lactis at a concentration of 25 percent and a possible very slight 
effect at 10 percent. The development was good at nearly 100 
percent, however, and only slightly atypical in character. There was, 
however, a slight tendency in the gas for the hyphae to grow upward 
and assume something of a tufted character. 
Cryptococcus Ludwigi. — ^This organism grew in all the percentages 
of the gas used, although slight inhibition occurred at 10 percent 
and the development was slight or very slight in the undiluted gas. 
With the inhibition of growth went also decrease in depth of color, 
so that in the case of the greatest inhibition the colony was practically 
colorless. The colonies in the gas up to 75 percent reached a maximum 
quite as great as that in the air but took a few days longer, while for 
colonies in an atmosphere containing more carbon monoxide neither 
this maximum nor the typical intensity of color was reached. Upon 
return to the air, however, these conditions were attained. 
Penicillium stoloniferum. — The lowest CO content at which growth 
was checked was 10 percent. At this percentage the checking was 
very slight, but increased with increase in the CO content, so that 
growth was very slow at 75 percent and above although conidia were 
usually produced, and if not they followed promptly on return of 
the culture to the air. 
