Figure 1: a) The prototype of the Macintosh laryngoscope. b) The current English Macintosh laryngoscope (size 3). Reference lines and points: line LN, a horizontal line drawn from the handlemounting block; point T, the blade tip; line TN, a line drawn from the point T perpendicular to the line LN; point M, a point of intersection of the line LN and under surface of the midportion and point F, a point of intersection of the line TN and extended line of the midportion. The line BN is the length of the laryngoscope. c) The overlaying image of the original design of the Macintosh laryngoscope on the radiograph laryngoscopy image. The black eyeline: with the current Macintosh laryngoscope; the white eyeline: with the prototype of the Macintosh laryngoscope.