LEAD POISONING

fumes, which was hardly noticed by the driver. Subsequent examination of the boot lid showed very slight staining, presumably with the carbon of the exhaust fumes, on the lefthand corner covering only about six inches. I then discovered quite conclusively that by having all the windows closed and the direct ventilator on that the problem could be overcome. I eventually overcame the problem more satisfactorily by carrying out the suggestion of Dr Wood of extending the exhaust pipe and directing it downwards. I think a corollary of this idea is a consideration of an accumulation of factors which could lead to drowsiness while driving, with possible accidents. The combination of factors, each small in itself is (i) smoking (which, I understand, produces about 5% carboxy haemoglobin in the blood); (ii) entry of exhaust fumes even in an apparently wellmaintained car; (iii) natural sleepiness on a long drive; (iv) altitude (915 metres to 1220 metres which is not uncommon on our roads would reduce the partial pressure of arterial oxygen about 8 mm Hg to 10mm Hg); (v) chronic obstructive lung disease, which could even reduce the partial pressure of oxygen in the arterial blood at sea level to 70 mm Hg in a person otherwise active; and (vi) last, but not least, a small amount of alcohol could be the last straw in this sheaf of factors. JAMES ISBISTER. 66 Pacific Highway, St Leonards, N.S.W. 2065.