AveusT 23, 1918] 
stant fraction of the amount of energy which 
the sense organ has received previously. 
vill 
Repeated stimulation of the kind just de- 
scribed, has frequently been called a process of 
adaptation to a stimulus. As such it has been 
used as a criterion for the presence of a 
“higher behavior” in many animals. Simi- 
larly, the fact that the reaction time continues 
to increase steadily has been taken to indicate 
a process of learning. 
The experiments forming the basis of this 
communication, have, however, shown that 
these phenomena are dependent on changes 
which take place within the sense organs them- 
selves. In addition, they have demonstrated 
that the process of “adaptation” to a photic 
stimulus in Ciona is subject to the course of a 
chemical reaction. The reverse of this reac- 
tion determines the ability of the organism to 
become “dark adapted.” Furthermore, the 
changes which occur in the reaction time dur- 
ing both of these adaptional processes are con- 
sistent with the principle underlying the 
Weber-Fechner rule. This requires that in 
order to act as a stimulus, the light must form 
a quantity of a substance such that it will bear 
a definite ratio to the amount of that substance 
already present in the sense organ. The matter 
of “higher behavior” is nowhere evident in 
these experiments. Setic Hecut 
PHYSIOLOGICAL LABORATORY, 
CREIGHTON COLLEGE OF MEDICINE, 
Omauna, NEBR. 
A METHOD FOR PREPARING PECTIN 
Pectin bodies is a term applied to a group 
of substances occurring in practically all 
plants and fruits. They are complex carbohy- 
drates, probably derived from one mother sub- 
stance known as pectose, and are closely allied 
to the plant gums and mucilages. Pectin 
occurs most abundantly in the apple, quince, 
currant and gooseberry and appears in small 
quantities in strawberries, raspberries, ete. In 
suitable amounts of sugar and acid the pectins 
have the property of gelatinizing fruit juices 
or hot-water extracts of fruit pulp in which 
SCIENCE 
201 
they are present or to which they may be 
added. The reason why some kinds of fruit 
juices do not jelly is due to an insufficient 
amount of pectin being present in them. For 
example the practise of mixing apple juice 
with raspberry or strawberry juice is for the 
purpose of increasing the pectin content and 
thereby make jelly from juices where it would 
be impossible to do so otherwise. The juices 
from the various kinds of fruits are known 
for their distinctive flavors. These qualities 
are impaired when a combination of juices are 
blended together. For this reason it has been 
the aim of manufacturers to make high- 
grade jellies from the low-containing pectin 
fruit juices by adding to them the purified 
pectin. The pectin, as now prepared, is very 
expensive and therefore its use in jelly-making 
is very limited. 
Pectin is slightly soluble in water and there- 
fore the pulp or pomace resulting from the 
pressing of ripe fruit contains practically all 
of the pectin. Hot water will slowly extract 
the pectin and for this reason fruits are-cooked 
to a pulp with water before extracting the 
juice for jelly-making. 
In the fruit-producing sections of the state 
of Washington, there is a considerable amount 
of cheap material such as cull apples, pomace 
from cider presses and cores and peelings 
from canning establishments which go to 
waste. This waste material might be utilized 
for the preparation of pectin which, in turn, 
could be used in making jelly from those fruit 
juices which lack pectin. The object of the 
experiment carried on in this laboratory was 
the finding of some simple and inexpensive 
process for the preparation of pectin from 
these waste products, without the use of al- 
cohol, as is the case in Goldthwaite’s! method. 
The principle of the method is based upon 
the fact that pectin as extracted from the pulp 
or pomace is in a colloidal state and can be 
readily changed by electrolytes. Since pectin, 
after precipitation, must be dispersed again in 
order to be of any value as a gelatinizing 
agent, an electrolyte that will produce a re- 
yersible precipitation must be chosen. Also 
1 J. Ind. and Eng. Chem., 2 (1910), 457. 
