QUESTIONS AND ANSWERS 117 



the lumen is granular; when the cells are exhausted, they are 

 smaller and remarkably clear, only a few granules being left on the 

 inner edge, whilst the lumen is now distinct and large and the 

 nuclei become large and rounded, showing the nucleoli. 



Compare the amount of saliva in the horse with that in the ox. On 



what conditions does the amoimt secreted depend? 



It has been estimated that the horse secretes 84 pounds and the 



ox 112 pounds of saliva in 24 hours. The amount depends on the 



dryness of the food, more being secreted when eating dry than moist 



foods. 



How is food when swallowed prevented from getting into the posterior 

 nares and the larynx? 

 The soft palate prevents food entering the posterior nares and 

 the epiglottis protects the larynx. 



Describe the phenomena of regurgitation in ruminants. 



Rumination is a reflex, nervous act and can only be performed 

 by means of the united action of the diaphragm, stomach walls and 

 abdominal muscles. It is performed as follows : The churning move- 

 ment of the rumen throws the food gently against the cesophageal 

 , groove, when a spasmodic contraction of the diaphragm and abdom- 

 inal muscles forces some of the liquid content of the reticulum and 

 the solid matter from the rumen into the oesophagus. The funnel- 

 shaped extremity of the latter contracts and cuts off the bolus, which, 

 by a reverse peristaltic action, is conveyed to the mouth. After a 

 thorough mastication, the bolus is reswallowed and passes directly 

 into the third compartment of the stomach. 



Explain fully why a normal horse can rarely vomit. 



1. The cardiac extremity of the oesophagus is thickened and 

 contracted. 



2. The oesophagus enters the stomach in an oblique direction. 



3. The dilated pylorus lies close to the contracted cardia, so that 

 compression of the stomach contents forces them into the duodenum. 



4. The mucous coat is thrown into folds over the cardiac opening. 



5. Encircling the cardia are muscular loops the contractions of 

 which keeps the opening tightly closed. 



6. The stomach is not in contact with the abdominal wall. 



State the function of the stomach. 



It thoroughly mixes the food and through the action of the 

 enzymes, secreted by its walls, converts proteid matter into pep- 

 tone, thereby rendering it absorbable. In young animals, there is 



