“…Rivaet al (1957), searching for defects of 1 centimetre or more, found an incidence of 13.8 per cent. Baker (1955) reported 17 per cent and Louros et al (1958) 12.7 per cent. These deficiencies do not always find their way into hospital records so that all authors stress the unreliable nature of recorded data on this particular point.…”