The head properties are of great importance and must be considered in proportion to the size of the dog. When viewed from the front or the side the head should bear a general resemblance to a well-blunted, clean wedge, being smooth in outline. The skull should be flat. The sides should taper gradually and smoothly from the ears to the end of the black nose, without prominent cheek bones or pinched muzzle. Viewed in profile, the top of the skull and the top of the muzzle should lie in two parallel straight planes of equal length, divided by a slight but perceptible "stop" or break. A mid-point between the inside corners of the eyes (which is the centre of a correctly placed "stop") should be the centre of balance in length of head. The end of the smooth, well rounded muzzle should be blunt, but not square. The underjaw should be strong, clean cut and the depth of the skull from the brow to the underpart of the jaw, should never be excessive (deep through). Whatever the colour of the dog, the nose must be black.