A RADIOGRAPHIC ANALYSIS OF MASTICATION AND SWALLOWING IN THE DOMESTIC RABBIT: ORYCTOLAGUS CUNICULUS (L)
*The Western Australian Museum, Perth, W.A.
- 1An analysis has been made of the movements of biting, chewing and swallowing in the domestic rabbit. Techniques employed were dissection, direct observation of rabbits feeding, cinematography, still radiography and cineradiography.
- 2During biting the lower jaw moves forwards so that the anterior and the lower incisors come together edge to edge. This observation casts doubt on Wood's theory that the lower incisor of the lagomorph is the lower homo-logue of the posterior upper incisor.
- 3Evidence has been given which suggests that the anterior upper incisors are worn and shortened by movement of the lower incisors upwards and backwards against their wear surface during biting. The transverse movement of the lower incisors during the grinding phase of chewing wears the posterior upper incisors and also maintains the chisel edge on the tips of the lower incisors. No movements have been seen whereby the remainder of the wear surface of the lower incisors is abraded: from examination of the teeth it is suggested that the level of this surface is maintained by being passed forwards across the cutting edge of the anterior upper incisors.
- 4During chewing the lower cheek teeth move from without inwards on the side on which chewing is taking place during the grinding phase.
- 5It appears that the tongue is functionally divisible into three parts: the diastemal portion is concerned with the procuring and manipulation of food and its passage backwards to the cheek teeth; the intermediate portion, which has a dorsal shield and lies between the cheek teeth, is responsible for placing the food on the lower cheek teeth and keeping it to the side on which chewing is taking place and passing it progressively backwards; and the posterior portion situated behind the cheek teeth is associated with the soft palate in providing temporary storage for chewed material prior to swallowing, and with the soft palate and pharyngeal musculature in swallowing.
- 6The tongue movements and swallowing mechanism in the rabbit are compared with those in man, lambs and kid goats.
- 7A functional theory to explain the evolution of the long diastema is put forward.
- 8Movements of the temporo-mandibular joint are also considered.