Figure 1.

Hartert’s thrombelastograph device (H-TEG). The cylindrical container (cup) is rotated through a total angle of 4.75° around the vertical axis. Light from a slit lamp is reflected onto photographic film that moves at a rate of 2 mm/min to record rotation of the rod (the film roll is 15 m long and 100 mm wide). In practice, lines between the dots on the film are not visible because the intensity of the light and photosensitivity of the film are configured so that the film is blackened only when the light is stationary, that is, at the point of maximum rotation of the cup when there is a 1-second pause in the oscillatory movement. Adapted from Hartert.⁶