South Africa [Images] batsmen Graeme Smith [Images] and Jacques Kallis [Images] had to go to hospital as fiery Australia [Images] paceman Mitchell Johnson [Images] caused havoc on the second day of the second Test on Saturday.

The left-arm fast bowler fractured captain Smith's little finger and also struck Kallis on the jaw as the home team limped to 138 for seven at the close, 214 runs behind Australia's first innings 352.

Smith retired hurt on two and is unlikely to bat again in the three-match series.

Left-hander JP Duminy [Images] did his best to withstand the ferocity of the onslaught as he compiled a composed 73 not out.

Johnson found top gear from the start, dismissing Neil McKenzie [Images] and Hashim Amla [Images] for ducks in the first over.

Medium-pacer Andrew McDonald also cashed in late in the day with three for 25.

Having bowled Paul Harris for four with the fourth ball of his second spell, McDonald then removed Kallis for 22.

South Africa's leading run-scorer returned to the crease at 104 for five after having three stitches below his chin. But he chipped his second ball to short mid-wicket where Ricky Ponting [Images] took a sharp catch.

McDonald breached Morne Morkel's [Images] defences in his next over, bowling him for two.

South Africa were then 106 for seven but Duminy and Dale Steyn [Images] (eight not out) made sure they reached the close without any further loss.

Johnson took three for 37 in 16 overs and has almost certainly killed off South Africa's hopes of winning the series, with Australia already 1-0 up.

He ended the second session by bowling Mark Boucher [Images] for one with a superb off-stump yorker and there was also a wicket for Ben Hilfenhaus [Images], who trapped AB de Villiers [Images] lbw for three.

South Africa had earlier claimed the last five Australian wickets for four runs as the visitors were bowled out four balls after lunch, Steyn snapping up the last two wickets to finish with three for 83.