DURING digestion experiments with cattle, it was observed that the animals never appeared to sleep and always used the same lying position. In recent years the behaviour of cattle and sheep has been carefully studied by numerous workers, particularly under grazing conditions; the subject has been reviewed by Tribe1 and Hancock2. In spite of this attention, the almost complete absence of reference to sleep is a striking feature of the reports. Brownlee3 could find no evidence that healthy cattle ever lost consciousness either by day or night. Similarly, Hancock4 found that it was debatable if cows ever sleep; even at times of total rest they kept their eyes open except for very short periods—a few minutes at most—when they generally rested their heads on the flanks.