38 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
Also, to make the experiments comparable with those of previous workers, 
the solutions, after digestion, were evaporated down to dryness before extraction and 
then extracted with dry ether. Moreover, to equalize, as far as possible, the amount 
of soap dissolved by the ether, controls were employed in which an equal percentage 
ot soap was added after evaporating the control (to which no soap had been pre- 
viously acided) to dryness. This was the method followed by Hamburger, who, 
however, did not add a definite weighed quantity of soap to the controls, but merely 
an approximately equal quantity. 
By this method the quantity of total ethereal extract is largely increased, but 
the control experiments, as well as the determinations of Series 3 {vide infra), showed 
that the increase was due to dissolved soap and not to neutral fat. 
Experiment 1. The intestinal mucosa of a cat was prepared as usual, and two 
quantities of 6 grammes each were weighed out. To portion No. 1, 30 c.c. of normal 
saline, o - 6 gramme of sodium oleate, and 0*3 gramme of glycerine were added ; 
and to portion No. 2, 30 c.c. of normal saline only were added. 
The two flasks were placed in the incubator for a period of forty-three hours 
at 3 6° C, and were then taken out and the contents evaporated to dryness in porcelain 
basins on a steam bath. 
When both were dry, o - 6 gramme of sodium oleate was added to No. 2, and 
then in each case four extractions were made with ether. The ethereal extracts were 
united in each case, the ether was evaporated off, and the two residues were weighed. 
Each residue was then dissolved in warm alcohol, and the amount of free fatty acid 
determined by titration with ^-alkali, using phenol-phthalein as an indicator. 
The results are given in the following table : — 
Weight of 
ethereal extract 
Weight of free 
oleic acid 
Difference 
Percentage of 
free oleic acid 
No. 1 
0-6290 
0-4399 
0-1891 
69-9 
No. 2 (control) 
O-^TOS 
O' 2 c 10 
O'l 198 
67-7 
Here it is obvious that a considerably greater percentage of oleic acid is 
extracted in No. 1 than in No. 2, on account of the previous hydrolysis, but the 
difference between total extract and oleic acid, as shown in the third column, is nearly 
equal in the two cases, there being a difference of only 69 milligrammes. Further, 
this difference is found in the opposite direction in the succeeding experiment 
( vide infra J, and hence lies within the limit of experimental error and does not 
indicate any formation of neutral fat. 
The considerable amount of oleic acid obtained in the control (No. 2) of this 
experiment, at first sight appears to indicate that ether is capable of extracting oleic 
