Vol.. 6, 1920 
CHEMISTRY: J. F. McCLENDON 
691 
samples are without apparent significance, but the average figures for each 
day show the contents to become less acid as the tube descended farther. 
The average figure for the 1st day was 10 2nd day 10 4th day 
10~^"S and 5th day 10 ^ The intestinal contents, when incubated at 
body temperature with boiled egg-white, showed hardly any proteolytic 
action. Probably egg-white requires to be swollen by the acid in the 
stomach before rapid proteolysis can take place. Egg- white will swell 
also in alkali, but the intestinal contents were near the isoelectric point 
of egg albumin, at which least swelling occurs. 
On taking a census of laboratory workers, I found they all considered 
the intestinal contents as being alkaline, and, in order to account for this 
erroneous impression, reviewed the literature since the days when physiolo- 
gists, ignorant of the germ theory, tasted body fluids to see whether they 
were acid or alkaline. Von Helmont, in 1648, found that the taste changed 
from acid to salt on passing from the stomach to the intestine. After the 
discovery of indicators, Tiedemann and Gemlin, in 1826, found that the 
soda from the common bile duct unites with the acid chyme and makes it 
less acid. In 1891, Macfadyen, Nencki and Sieber, with the aid of a grant 
from the Elizabeth Thompson Science Fund, studied the outflow from a 
fistula in the ileum of a patient continuously for 6 months and found it 
always acid. It seems strange, therefore, that the popular notion is that 
the intestine is alkaline and I cannot account for this unless it is due to 
the fact that the secretions of the pancreas and the glands of Brunner and 
Lieberkuhn in the intestine are alkaline as shown by titration and with 
the hydrogen electrode. They are not sufficiently alkaline to neutralize 
the acid chyme. 
My determinations were made with the hydrogen electrode and after 5 
years' experience with biological fluids, I have begun to feel confident 
of determinations without the precaution of triplicate and quadruplicate 
samples. Palladium electrodes are attacked by acid of the stomach and 
sometimes of the duodenum. I use gold electrodes plated bright with 
iridium. By using a very concentrated solution of iridium chloride the 
plating can be done in about 2 minutes, and the electrode may be used 
longer without replating than when plated with platinum, and is easier 
to clean because it is bright. In non- viscous fluids the electrode must be 
entirely immersed in the sample, and the latter kept saturated with hydro- 
gen gas by shaking. The presence of oxygen gives a low voltage to the 
hydrogen-calomel cell. In such cases the voltage rises after the shaking 
has ceased. The acidity of the intestine aids in the preservation of the 
antiscorbutic vitamine while it is being absorbed. Feeding of lactose 
changes the intestines of guinea pigs from alkaline to acid. 
