330 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Ruminant animals are very timid and easily frightened, so very 

 slight causes will arrest rumination. As soon as the attention is 

 attracted the animal abruptly ceases to ruminate, and if lying down 

 rises and often runs away. A sudden sound, a falling object, or some 

 strange sight may be sufficient for this, although, of course, animals in 

 domestication become less impressionable. Slight maladies prevent 

 rumination, as do excessive food and gases in the stomach, venomous 

 or narcotic plants, forced marches, fatigue, rut, and suffering of all 

 kinds. Even the separation of a mother from her young has been 

 known to temporarily arrest rumination. The longer rumination is 

 postponed, the more difficult is its recommencement, since food becomes 

 dry and compactly packed in the rumen and the inam^plies, and their 

 membranes become irritated. 



It would appear at first sight as if the act of rumination was a 

 purely voluntaiy process, since the least psychical disturbance inter- 

 feres with its accomplishment. Nevertheless, like other complex co- 

 ordinated movements, such as deglutition and defecation, which are par- 

 tially under the control of the will, rumination is essentially reflex in 

 nature, and has for its point of departure the irritation of the terminal 

 filaments of the sensory nerves of the rumen. The centripetal path 

 of this nervous impulse lies in the pneurnogastrics, and explains the 

 suspension of rumination when these nerves are divided ; the automatic 

 nervous centre is located in the medulla oblongata, its precise position 

 being, however, unknown ; the efferent nerves are the motor nerves of 

 the stomach, diaphragm, and abdominal muscles, together with the 

 nerves going to the muscles of mastication and deglutition, and to the 

 parotid glands. 



In goats narcotized with morphine Luchsinger was able to produce 

 all the movements of rumination by artificially stimulating the sensory 

 nerves of the rumen, either by pressure with the hand on the surface 

 of the rumen, electrical stimulation, or distensions by injections of warm 

 water. He also found that not only might the regurgitation and ascent 

 of the bolus be so produced, but that movements of mastication and 

 deglutition and salivation were produced even when by division of the 

 oesophagus the ascending bolus was prevented from reaching the mouth, 

 thus indicating that these processes also are gastric reflexes. 



Rumination may thus be regarded as a species of vomiting, modified 

 in such a manner that there is no escape of the ejected matters from the 

 mouth, and that no more is regurgitated from the stomach at any one 

 time than can be conveniently masticated ; for as soon as the bolus 

 engages in the gullet the oesophageal pillars become firmly contracted 

 and the gastric orifice of the oesophagus remains closed until the cud, 

 having been subjected to a second mastication, again enters the stomach. 



