CAREY: GROSS STRUCTURE OF AN AGAR GEL 181 
more hydrated the gel is. Fischer* accounts for the condition 
found in the tissues in oedema by means of syneresis, and Mac- 
Dougal} considers syneresis as a means of vacuole formation 
after which osmotic pressure plays its part, the earlier stages 
being due to hydration. 
Fic. 4. A 7.5 per cent agar gel after drying at about 70° C. and soaking in water, 
Zsigmondyt states that, if the reaction of dehydrated silicic 
acid gels toward hydrosols is observed under the microscope, 
the gel will be seen to break into small pieces. This, he says, is 
* Oedema and nephritis. 1915. 
Growth in organisms. Science II. 49: 599-605. 1919. 
t Chemistry of colloids. English edition. 1917. 
