Thrombus formation on cannulae.

Seven types of cannulae were inserted into the cephalic vein of sheep which were killed after 1, 3 or 9 days so that the mass of thrombus associated with each cannula could be measured. Statistical analysis indicated that there was a statistically significant difference of greater than 2-fold between types of cannulae in the amount of thrombus. Differences between the 3 periods were not significant.