With the latest type of Astrup machine ABL4 we studied the temporal dynamics of blood-testing immediately following the taking of the blood-sample and then after 30 minutes, 3, 6 and 8 hours. After suitable storage of the samples (in a refrigerator at a temperature of +5 degrees C) we did not record any statistically significant differences in the values of the acid-base indices of blood after any interval of time. After testing the Radiometer hypodermic syringe, which the manufacturer supplies for the taking of arterial blood-samples from humans, it was shown that it was also completely suitable for taking venous blood-samples from animals. After application of a glass bead and mixing, the blood did not congeal even after eight hours. Testing both Radiometer and Rekord syringes for the taking of blood-samples, we ascertained that the results pointed to the suitability of both in ascertaining the acid-base values in all the intervals of time studied by us.