SEPTEMBER 27, 1918] 
absorb water still depends upon their respec- 
tive water-contents when they were made up, 
as Table I. shows. Several lots were made up 
to the concentrations given in the heading of 
the table, poured out on glass slabs, and 
allowed to lose water by evaporation at room 
temperature until tests showed that all had 
attained the same water-content (one gram 
gelatine to 0.17 grams water). Then pieces of 
the same size and form were placed in dis- 
tilled water and their increase in thickness 
measured at intervals. The table shows that 
the lot which had the highest original per- 
centage of water, increased in size most 
rapidly. That this meant a real difference in 
the amount of water absorbed was shown by 
the tests of the water-content at several stages. 
After 136 hours the pieces which were orig- 
inally made up to contain 11 per cent. gelatine, 
had a water content of 98.4 grams per gram 
of gelatine. At the close of 160 hours the 
original 20 per cent. gelatine contained 178.0 
grams of water per gram of gelatine, and the 
33 per cent. gelatine, 100.0 grams of water per 
gram of gelatine. 
The above results indicate that the evap- 
oration of water from the gelatine influences 
any subsequent absorbing rate. The evapora- 
tional history of the gelatine used affects also 
the distribution of the increase in size among 
the several dimensions of any given piece, as 
is shown by the following conclusions which 
have been drawn from a large number of ex- 
periments. The tables to which reference is 
made contain fair samples of the many read- 
ings taken. The tests were made upon gel- 
atine of several concentrations varying from 
10 per cent. to 33 per cent. The pieces re- 
ferred to were rectangular blocks 2.00 < 0.35 
X 0.35 em. 
1. When no appreciable amount of water 
has evaporated from the gelatine since it has 
set, blocks swell equally in length, thickness 
and breadth. This is true whether five min- 
utes or forty-eight hours has elapsed since the 
setting. See Table II. 
2. These blocks, when placed on a glass 
plate with their largest faces in a horizontal 
position, and allowed to lose water by evap- 
SCIENCE 
325 
oration at 18° to 30° C., shrink about twice as 
much in the two short dimensions as in the 
long one, shrinking being calculated as per- 
centage of original size. See Table IT. 
3. When the blocks which had received the 
treatment mentioned in paragraph 2 above, 
were placed in water and allowed to swell the 
distribution of amount of increase among the 
three dimensions was in the same ratio that 
the shrinking had been. That is, the increase. 
in size was about twice as great for the two 
short dimensions as for the long one. This 
distribution of increase continued for at least 
60 hours after the gelatine had attained its 
original water-content. See Table II. 
4, When blocks were cut from freshly made 
gelatine and hung on a thread with the long © 
axes in a vertical position, where they were 
exposed to the air on all sides, the same dis- 
tribution of decrease in size among the several 
dimensions took place as was described under 
paragraphs 2 and 3 above. The subsequent 
increase in size when blocks were placed in 
water also showed the same relation as for- 
merly. That is, the shrinking and subsequent 
swelling were about twice as great in the two 
short dimensions as in the long one. 
5. When gelatine was poured into a large 
dish or on to a glass slab and allowed to lose 
water by evaporatidn before pieces were cut, 
the decrease in thickness far exceeded the de- 
crease in the other directions and the subse- 
quent swelling in water followed the same pro- 
portions. For example, 15 per cent. gelatine 
when treated in this manner showed swelling to 
the following amounts: Height, 181 per cent., 
breadth 15 per cent., length 6 per cent. For 
the behavior of 33 per cent. gelatine see Table 
Tif. The more water lost by evaporation, the 
greater the difference in the swelling of the 
heighth and the other dimensions. 
The above results indicate that the evapor- 
ation of water from the surface of gelatine 
jelly changes in some way the physical struc- 
ture of the jelly. There has appeared thus 
far no evidence to determine whether these 
changes concern small group of molecules or 
much larger masses of gelatine. It may be 
merely that evaporation taking place more 
