The Digestive System. . 41 



marked dividing line and as a result two varieties of 

 mucous membrane, the one a continuation from the gullet 

 with no secreting glands in it, the other, or villous por- 

 tion, the true digestive coat containing the gastric glands. 



It is a good idea to consider the first three divisions of 

 the ruminant stomach as a widening out of the gullet. 

 The capacity of a horse's stomach is about 3 to 3% gal- 

 lons, that of the paunch (first stomach) of a cow 45 to 60 

 gallons, of a sheep' s paunch 10 to 15 gallons, and of a 

 pig's stomach 1^ to 2 gallons. 



The process of rumination, although carried out with 

 the assistance of the first three stomachs, is not a pure 

 digestive act, but merely preparatory, hence we consider 

 it as part of stage one. In some animals the food when 

 swallowed is finely divided enough to be acted upon by 

 the gastric juice in the true stomach, in others it has to 

 be mixed and churned up with the mouth saliva in order 

 to soften it before its return to the mouth for remastica- 

 tion. In birds digestion starts at once, although the 

 food may not be finely ground. The process of returning 

 the food to the mouth for a second chewing, known as 

 rumination, is peculiar to the many-stomached herbivora 

 (grass eaters). This process differs from vomiting, in 

 that it is partly under the control of the will, in fact the 

 one is abnormal (unnatural), the other normal (natural). 

 If rumination stops for any length of time the cause 

 should be looked for; as has been pointed out, the pro- 

 cess consists of the passage up and down the gullet of 

 food from the stomach; therefore, the giving of an ani- 

 mal a cud (so-called) is a ridiculous practice, and one 

 that cannot be expected to restore the natural movements 

 which are in abeyance. 



