The shape of the skull, particularly in brachycephalic breeds such as the bulldog, can lead to a variety of clinical conditions, e.g. snoring respiration, difficulty in breathing.

The relative size of the head can also cause difficulties with whelping. Breeds with a mesaticephalic shape of skull are much less likely to exhibit these conditions.

1. Dobehocephabe - the head, particularly the nose, is long and narrow, e.g. Greyhound. Borzoi. Afghan hound

2. Meiatkephalk - (mes meaning 'middle') is the 'normal' or average shape of the dog skull, e.g. Beagle, Labrador. Pointer

3. Brachycepholk - the cranium is often more rounded and the nose is short and may be pushed in, due to shortening of the nasal chambers, hard palate and mandible, e.g. Bulldog, Pekinese, Boxer, Pug.