736 
Journal of Agricultural Research 
Vol. V, No. 16 
titrated — 8. The culture grew vigorously for a week or two, formed a 
mat and some aerial mycelium, then the gradual checking of the growth 
occurred. The culture ceased producing aerial mycelium and the mat 
became half submerged. Soon all growth ceased and the culture grew 
but indifferently or not at all when transplanted. 
If old pea-broth cultures were acidified to approximately +5 with 
potassium acid phosphate, tartaric acid, or hydrochloric acid, growth 
started again and pycnidium production took place upon the dense 
mat. 
Other media showed similar changes in either acid or alkaline reac¬ 
tion, and, as a rule, it may be said that media with a proportion of pro¬ 
tein lower than the carbohydrate proportion show after a period of 
growth an acid reaction (Wehmer, 1891). With media high in pro¬ 
tein the reaction becomes alkaline (Nageli, 1880). 
The consideration of the acidity or alkalinity of substrata at the start 
and at the close of a period of culture leads naturally to a consideration 
of autointoxication. This is especially appropriate in this case, since 
the autointoxication effects observed were due to harmful reactions 
produced by the by-products of metabolism. These by-products were 
not of the complex type commonly thought of in connection with the 
term autointoxication, but were mostly the simple and well-known end 
products of carbon and nitrogen dissimilation. The injurious effects 
were produced to a large extent by the acidity or alkalinity engendered, 
and the same effects could be artificially produced in a favorable medium 
by mere change of reaction. 
Depending upon the excess of carbohydrate or protein, as has been 
said, the reaction of the substratum became either acid or alkaline. In 
the case of excess of carbohydrate, oxalic acid is formed by this organism, 
and in old cultures of corn, oats, or prune-juice agar crystals qf calcium 
oxalate were often found. In the case of protein excess, as was demon¬ 
strated for old pea-broth cultures, the medium contained an excess of 
ammonia. This ammonia could be detected by boiling the liquid from 
such old cultures and testing the fumes with a strip of wet, red litmus 
paper. 
In a solution where the carbohydrates and protein constituents are 
present in a proper ratio, these by-products of metabolism neutralize 
each other. Com broth is a notable example of this type of medium, for 
in it the by-products, even after two months, are not potent enough to 
interfere with reproduction. 
The action of these autointoxication products in the substratum is 
further illustrated by the common experience met with in transferring 
from old cultures of this organism. In old agar cultures of various sorts 
the mycelium was found dead when it was submerged in the sub¬ 
stratum, although the aerial mycelium remained alive for more than a 
year. 
