14 BULLETIN 158, U. S. DEPARTMENT OF AGRICULTURE. 
were able to convert adenine and guanine into hypoxanthine and 
xanthine. They also show that the bacteria have the power of spHt- 
ting the nucleic acid itself. This same change is also brought about 
by the action of certain enzymes, such as erepsrn, on nucleic acid. 
With these facts at hand it is possible to draw the following con- 
clusions as to the source of the two purine bases in this fertilizer: 
The guanine and hypoxanthine may be derived from plant remains 
which originally contained these two compounds; the guanine may 
arise by the acid hydrolysis of certain vegetable or animal nucleo- 
proteins which were present in the original materials; and the 
hypoxanthine may have been formed by the processes of natural 
decomposition, such as the action of bacteria and enzymes, which had 
taken place in the crude materials before they were subjected to the 
acidulation process or during the process itself. It is not improbable 
that the guanine and hypoxanthine come from all of these sources. 
Diamino acids. — Of the three diamino acids lysine was obtained in 
much the largest amount, arginine next, and histidine in the smallest 
amount. These compounds are products of protein hydrolysis by 
acids, but may also be produced under certain conditions by the 
action of bacteria. Siuce one or more of the diamino acids have 
been found to be present in every protein so far examined, and since 
the method for the analysis and the isolation of these bases is almost 
quantitative, the determination of the number and amounts of the 
diamino acids present in a mixture of protein hydrolysis products is 
of importance lq deciding the nature and character of the original 
material which entered into the processed goods. 
Monoamino acids. — Although leuciue and tyrosine, which are pro- 
tein decomposition products, were found in about the same quanti- 
ties, the methods of isolation were so far from being quantitative 
that this relationship is of no significance. The isolation and identi- 
fication of the other monoamino acids from the complex products of 
proteia hydrolysis can only be accompHshed, m the majority of 
cases, by means of the esterification method of Emil Fischer. This 
method is not a strictly quantitative one and requires large amounts 
of materials for a successful separation, and consequently was not 
used in this iuvestigation. The use of methods other than that of 
esterification failed to isolate any other monoamino acid in quantities 
large enough for identification. As will be shown later, a number of 
monoamino acids besides the two isolated must be present in the 
processed goods. 
Estabhshing the presence of these products of acid hydrolysis of 
proteins, namely,* the diamino acids, arginine, lysine, and histidine, 
and the two monoamino acids, leucine and tyrosine, in the amoimts 
in which they were found is of itself sufficient evidence to demonstrate 
that by the acid treatment of the crude materials used in the manu- 
