Ten blindfolded soldiers move haltingly in a single file across the twentyfoot-long canvas in John Singer Sargent's Gassed (1918–19), each touching the man in front (Figure I.1). What each soldier perceives is what the hand feels – rucksack, rifle or the rough uniform-clad body in front. The hand not only grasps or clutches; it enables the soldiers to think and plan the next step forward, gathering a cluster of disabled men into a neat line. The sense of touch defines space and guides the rhythm of their movement, as if new eyes have opened at the tip of the fingers. Sound is implicitly there, in the form of noises of the football match played in the distant background or the flock of aeroplanes whirring above the parallel file of soldiers towards the top right-hand corner of the painting. But rushes of sound are subsumed into the tactile continuum joining the figures in the file as well as those heaped on the ground. Painting, like surgery, requires a rare co-ordination of the eye and the hand. Every fresh brushstroke is a guiding and manoeuvring of touch on the canvas just as each little movement of the blindfolded soldiers in the painting is sensed through the hand. The interruption of the chain by the fourth soldier from the end as he temporarily falls out of line draws attention to the centrality as well as the nakedness of the hand.