The mammary blood flow in the cow as measured by the antipyrine absorption method.

After intramammary application of 3 g antipyrine dissolved in 30 ml distilled water into each quarter the absorption of antipyrine from the udder proceeds as a first order reaction. As the injected amount is known as well as the amount of antipyrine milked out about 1 hour later can be determined, it is possible to calculate the amount absorbed at any time between injection and emptying. It is shown, that the concentrations of antipyrine in the blood from the jugular vein and external pudic artery are identical after intramammary application of antipyrine. In experiments on lateral recumbent cows it is shown that the venous blood returns from the udder via both the subcutaneous abdominal and the external pudic veins. In the standing cows blood samples were drawn from the jugular and the subcutaneous abdominal veins. The blood samples from the subcutaneous abdominal veins were drawn during manual compression of the external pudic veins to get representative concentrations of antipyrine in the total venous blood from the udder. On account of the amount of antipyrine absorbed and the difference in antipyrine concentrations between the subcutaneous abdominal veins and the jugular vein the mammary blood flow in lactating cows was found to vary between 22–101 ml/min. per 100 g gland tissue. The possibility of calculating the mammary blood flow after injection in two glands only — while the two remaining glands might be used for other studies — is shown and discussed. The influence of the individual differences in the venous anastomoses on the results is discussed, and a procedure is described to select cows suitable for experiments on mammary blood flow.