(961 ) 
property of some solid substances, which under the most powerful 
microscope do not show visible pores, to occlude liquids between 
their smallest particles. If they are examined again after the absorp- 
tion of the liquid it is impossible to distinguish the separate particles 
of the liquid and the solid substance even when using the most 
powerful lenses. 
During this absorption of liquid the smallest particles of the solid 
body are separated from each other by the penetrating molecules of 
water. ReriNKe has called this increase of the distance between the 
particles the dncrease of disgregration of the solid substance. Because 
those particles get at a greater distance from each other, the volume 
and length measurements of the solid body suffer an increase *) ; 
henee the name “swelling”. At the same time the cohesion between 
the particles of the solid substance appears to have much decreased *). 
On the other hand we may expect that there will exist a great 
affinity between the water and the solid body if this is able to 
overcome the so powerful cohesion of the solid substance. This 
suspicion is confirmed; during the swelling a considerable amount 
of heat is liberated *) and an important contraction of volume takes 
place, in other words, the volume of the swollen body is considerably 
smaller than the sum of the volume of the solid substance and that 
of the imbibed water. 
On drying, the swollen bodies can again part with the liquid 
absorbed; if this takes place slowly the homogeneity is retained. The 
phenomenon is at least in the main -— reversible. 
Some swelling bodies, such as casein, wood, ete. when placed in 
contact with saturated water vapour absorb only a limited quantity 
of water and a so-called maximum of imbibition is reached (bodies 
of limited imbibition power); others such as gum arabie and peptone 
take up an unlimited amount of water causing them to become more 
and more fluid so that they, finally, get converted into a liquid 
mixture of water and imbibing substance (bodies of unlimited imbibition 
power). 
agree with him. The above definition is borrowed from HuGo pe Vries, Leerboek 
der Plantenphysiologie, 4e Ed, p. 149-150 and from H. A. Lorentz, Leerboek 
der Natuurkunde, 2e Ed, Vol. I, p. 419. 
1) Sometimes very considerably; peas double in size, Lrish moss (Chondrus 
crispus) swells to treble its size. (HUGO pe Vrirs, loc. cit, 4e Ed. p. 150). 
2) Remke (loc. cit. p. 31) found that if air-dry Laminaria absorbs 300 °/, of 
water its ductility increases sixty fold while the breaking strain falls to one-tenth 
of its value. 
3) If amylum tritici, dried at 90°, is stirred with its own weight of water, the 
temperature rises more than 10’ (NäceLr, Theorie der Gährung, (1879 p. 133-134) 
