On the Size and Growth of the Blood in Tame Rats

(1) The average oxygen capacity per kilo of the rat between 50 and 150 grammes is 10·0 c.c., and the average blood volume per kilo 63·0 c.c. The average Hb percentage is 86, and the number of red cells 9 million per cubic millimetre. (2) There is a temporary fall in the Hb percentage, oxygen capacity per kilo, and blood volume per kilo during the suckling period, and a second fall in the oxygen capacity per kilo and the blood volume per kilo in later life connected with the diminished rate of growth in larger animals. (3) The oxygen capacity per kilo is less variable than the percentage of Hb blood volume per kilo or number of red cells per cubic millimetre. (4) The volume of the blood is less variable than the weight of the kidneys, liver, and spleen, considered as percentages of the total body weight. (5) The volume of the blood in rats may be calculated by the formula body weight0·9/10·1 = volume, and the total oxygen capacity by the formula body weight0·95/8·0 = total oxygen capacity.