26 GENERAL THERAPEUTICS FOR VETERINARIANS 



the therapeutics of diseases of the stomach will vary according to 

 whether the disturbance of digestion originates in the muscular 

 action and innervation of the stomach wall, in the gland secretions 

 and chemical properties of the gastric juice, or in decomposition of 

 the stomach contents. Accordingly, treatment may be required 

 for the muscles, the glands, or the contents. From a therapeutic 

 standpoint, the following physiological facts are of importance: 



1. Mechanism of the Stomach. — In the horse, as well as in 

 the other domestic animals with a single stomach (dog, hog, cat), 

 the pylorus and cardia close immediately after a meal, and remain 

 closed for a time. Then, the muscular layer in the stomach wall 

 begins to contract, the pylorus is opened simultaneously, and the 

 contents of the stomach are gradually emptied into the intestines. 

 A part of the food and water ingested at this time, likewise of any 

 medicines administered, pass directly into the intestines without 

 detention in the stomach. This explains why medicines given by 

 the mouth are sometimes surprisingly prompt in their action 

 (cathartics, acetanilid, anthelmintics). The opening of the pylorus 

 appears to be caused reflexly by the stimulant action of the gastric 

 juice secreted and collecting in large amount. In addition, stimuli 

 originating in the duodenum also operate to empty the stomach. 

 In a similar way, other stimulants (alcohol, veratrum, oil of tur- 

 pentine and spices) act reflexly through the intestines as well as the 

 stomach and accelerate the opening of the pylorus and the empty- 

 ing of the stomach. 



The normal period of retention of food in the stomach differs 

 greatly with the kind of food, the method of feeding and the ani- 

 mal species, as well as with the individual, in horses, after a 

 small meal of oats, the passage of the contents of the stomach into 

 the intestines begins in 2 to 3 hours and continues for more than 12 

 hours. Drinking water during or immediately after eating hastens 

 the passage of the material in the stomach into the intestines. 

 Water alone or fluid medicines, on the contrary, pass through the 

 stomach of the horse very quickly; part in a few minutes. Exer- 

 cise, especially trotting, retards the emptying of the stomach of the 

 horse. 



