7 
decomposition brought about by the blood of man and the higher ani- 
mals, and that the blood of fishes possesses the least catalytic activity 
of any blood thus far examined. It has also been observed that the 
power of the blood of man to decompose hydrogen peroxide suffers a 
marked diminution in certain pathological conditions such as tubercu- 
losis, nephritis, and cancer. The} 7 have found further that the catalase 
of blood is destroyed by boiling, and also by acids; that it is present 
exclusively in the formed elements of the blood, and that roughl} 7 , at 
least, it is proportional to the amount of hemoglobin. 
Sometime ago, it was observed by one of us (Kastle) that the yel- 
lowish filtrate from boiled blood has the power of effecting the oxida- 
tion of phenolphthalin in alkaline solution, whereas, solutions of blood 
salts, with and without iron, prepared according to the analyses given 
in Bunge’s Physiologic and Pathologic Chemistry (pp. 212-213), do 
not possess this property. Up to the present, we have not had an 
opportunity to investigate this interesting difference in conduct of 
these two solutions. It led to the notion, however, that it would 
probably be of interest to determine the oxygen-carrying power of the 
blood in alkaline solution under various conditions of health and dis- 
ease, using phenolphthalin as the oxidizable substance and hydrogen 
peroxide as the oxidizing agent. In other words, the attempt has been 
made to determine what ma} 7 be called the peroxidase activity of the 
blood of man under various conditions of health and disease. 
4119— No. 3]— 06— 2 
