384 Urea and Ammonia in Placenta 
standardized conditions of aeration, enzyme action, and quantity 
of carbonate used, the changes in the ammonia content of the 
tissue during standing while undergoing fermentation introduce 
a considerable error. 
Folin and Denis (10) early pointed out that the ammonia content of 
drawn blood increased if the sample was allowed to stand. Although 
Mateer and Marshall (6) have definitely directed that in the determina- 
tion of urea by the urease method ammonia determinations need to be 
made simultaneously and similarly, only excluding the urease prepara- 
tion, various published reports have failed to mention or consider am- 
monia determinations; Slemons and Morriss (11) have even gone so far 
as to state that such analyses yield insignificant results. 
TABLE III. 
Increase in the Quantity of NH; Recoverable from Placenta Tissue after 
Standing Half an Hour. 
NHs3 in 100 gm. of tissue. 
Immediate. After 3 hr. 
mg. mg. 
&> 
wMww)8OowWwoON 
ew RP DNw SN 
Oo OHO Om 
me mem GC N Or 
In order to determine whether or not there was any marked 
difference between the ammonia obtained by immediate aeration 
and that given off from the placenta tissue after it had stood for 
1 hour in suspension in the test-tube, a series of tests was made, 
the results of which are found in Table III. 
It is evident that increases in the ammonia content of the tissues 
ranging from 14 to 85 per cent may occur, which alone indicates 
the necessity of allowing the tissue from which the ammonia 
values are to be determined, as a basis of the analysis for urea, 
to stand under similar conditions as do those samples in which 
the urea is undergoing splitting by the urease. 
The results reported in this work are based on parallel deter- 
minations and have an average variation. of 2 per cent. 
