254 
GEOFFREY SMITH. 
of caustic potash is added and the mixture is heated on a 
water-bath for about half an hour. About 10 c.c. of alcohol 
are added and the heating is continued for another hour. By 
this process the proteid material of the blood is largely broken 
down and all the fat and lipoid substances are converted into 
soap. The saponified mixture is now washed with hot water 
into a long- necked flask, and a sufficient quantity of 40 per 
cent, sulphuric acid is carefully added until the reaction is 
distinctly acid. By this means the fatty acids are liberated 
from the soaps. After cooling, 40 c.c. of pure ether petroleum 
are added, and the flask, after being stoppered, is shaken for 
about an hour. The fatty acids are taken up by the petroleum, 
and water is added to the flask until a clear column of 
petroleum is obtained in the neck of the flask. Ten or 20 c.c. 
of the petroleum is accurately pipetted off and evaporated to 
dryness in a weighed beaker. The weight of the residue in the 
beaker gives the amount of etlier-soluble substances contained 
in the blood, after saponification and liberation of the fatty 
acids, and may be taken as giving a fairly accurate estimate 
of the amount of fat and lipoid in the original blood. There 
are certain experimental sources of error in this method, but 
by always taking nearly the same amount of blood and 
treating it in the same way, the comparative estimate afforded 
for different types of blood is reliable and has given very 
constant results, as the subjoined table shows. 
The ethereal extract on evaporating to dryness yielded a 
golden yellow or orange waxy substance, soluble in alcohol 
or ether, as a clear yellow or orange solution. The chemical 
nature of the fat and lipoid substances contained in this 
material will be the subject of future investigation. 
The following 1 points, however, which were made out with 
the assistance of Dr. Ramsden, are sufficient to indicate the 
nature of the substances dealt with. A weak ethereal solution 
of the extract from the pink blood gives when examined 
spectroscopically an absorption band on the F line of the 
spectrum, while the yellow lipochrome in solution gives in a 
suitable dilution two bands, one at the F line and another 
