Inorganic phosphate values of plasma and red cells from parasitized monkey blood are lower than normal. Plasma potassium values are higher than normal particularly during segmentation. Other inorganic components of parasitized blood show little variation from normal.

2. Monkey red blood cells parasitized with P. knowlesi consume oxygen in the presence of glucose, lactate, glycerol, and amino acids as substrates. Their respiration is inhibited by cyanide, carbon monoxide, and high oxygen tensions. Normal monkey red blood cells consume oxygen at an appreciable rate only in the presence of methylene blue.

3. Parasitized erythrocytes convert glucose to lactate at a rate 25 to 75 times that of the normal monkey erythrocyte. Unlike the normal red cell, the parasitized cell utilizes lactate if oxygen is present. Lactate is utilized, however, at a rate that is only one-sixth that of its production from glucose.

4. The significance of these findings in relation to the problem of cultivation of malarial parasites is discussed.