326 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



infuudibulum of the oesophagus, and while it is due to the contraction 

 of the auxiliary organs, this contraction is not, under ordinary circum- 

 stances, very energetic, but becomes so when, as a consequence of 

 various diseases, the food in the rumen becomes more or less dry. The 

 ascent of the cud is not only due to the pressure of the contracting 

 abdominal and gastric muscles, but aspiration to a certain extent assists 

 its onward progress. At the moment of the act of rumination the glottis 

 is closed, and as the diaphragm contracts the thoracic capacity is 

 augmented and the bolus is drawn toward the thorax. "When, and as 

 soon as the bolus of food is- engaged in the oesophagus, it is carried to 

 the mouth with great rapidity by the action of the muscular fibres of 

 the oesophagus, the process being the reverse of deglutition; that is, the 

 longitudinal fibres first contract, and so widen the oesophagus, and then 

 the circular fibres successively contract below the bolus, and so force it 

 upward. The ascent of the cud is visible throughout the entire length 

 of the neck in most ruminants, particularly in those which are thin, or 

 which, like the camel, have a long neck. Its ascent is also perceptible to 

 the touch and to the sense of hearing. When the ear is placed over the 

 course of the oesophagus in a ruminant animal, various sounds may be 

 recognized during the act of rumination. In this position bubbling or 

 moist friction sounds can be heard from the region of the rumen, even in 

 the intervals of the rumination, due to the disengagement of bubbles of 

 gases in the process of fermentation which so often occurs in this viscus. 

 These sounds are most marked in animals which are fed on green fodder. 

 A sound very closely analogous to the pleural friction sound is also 

 heard in the same locality coincident with the movements of respiration. 

 It is due to the friction between the rumen and the diaphragm. The 

 peculiar bubbling sounds due to the motion of foods may also be heard, 

 and are dependent upon the entrance of saliva or food into the first and 

 second stomach and the passage of currents from the first and second 

 stomachs, and vice versa. In addition to these, rumbling and churning 

 sounds, due to the motion of the material in the rumen and produced by 

 contraction of the pillars of the rumen, may also be heard. During 

 active rumination, if the ear is placed over the cervical path of the 

 oesophagus, that is, over the left jugular, the passage of the bolus may be 

 distinctly heard. The ear perceives the tactile impression of a body 

 passing rapidly beneath it, and a sound is heard which by its peculiar 

 characteristics indicates that the bolus is impregnated with or accom- 

 panied by a quantity of liquid. 



As soon as the bolus- enters the mouth, a second sound is heard 

 ■which indicates the rapid downward passage of liquid. This may be 

 repeated two or three times at short intervals, and shows that the bolus 

 is accompanied in its ascent by a quantity of liquid, which, as soon as its 



