CHEMICAL PROPERTIES OF HAY INFUSIONS Diets 
Fig. 4 Infusion C-31, illustrating maximum difference in cultures of series C 
between ‘phenolphthalein acidity’ of top and bottom of infusion. Ordinates 
represent number of cubic centimeters of 0.01 N NaOH per 100 ce. of infusion. 
Top = ————-; bottom = ----- . 
sions of the C series present quite a different condition. Here 
untreated hay is covered with clear water. There is the oppor- 
tunity for the formation of a concentrated solution of hay con- 
stituents at the bottom, which serve for the development of a 
high degree of acidity. During the first few days there is a rela- 
tively concentrated solution at the bottom with a corresponding 
high acidity, while at the top of the infusion both these conditions 
are reversed. As diffusion proceeds, the concentration approaches 
uniformity and hence acidity differences tend to disappear. Uni- 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 12, No. 2 
