OH. XXXV.] MOVEMENTS OF THE STOMACH. 5 21 



oesophagus with motor, and the cardiac sphincter with inhibitory 

 fibres. If food is swallowed after these nerves are divided, it 

 accumulates in the gullet and never reaches the stomach. 



In discussing peristalsis on a previous occasion (p. 161), we 

 arrived at the conclusion that it is an inherent property of 

 muscle rather than of nerve ; though normally it is controlled 

 and influenced by nervous agency. This nervous control is 

 especially marked in the oesophagus ; for if that tube is divided 

 across, leaving the nerve branches intact, a wave of contraction 

 will travel from one end to the other across the cut. 



Swallowing of Fluids. We must next note that the swallow- 

 ing both of food and drink is a muscular act, and can, therefore, 

 take place in opposition to the force of gravity. Thus, horses 

 and many other animals habitually drink up-hill, and the same 

 feat can be performed by jugglers. 



Under ordinary circumstances, however, the swallowing of fluids 

 is differently produced from what we have already described : 

 the division of the act of deglutition into three stages is true 

 for the swallowing of solids only. This has been shown by 

 Kronecker. 



In swallowing liquids the two mylo-hyoid muscles form a 

 diaphragm which pulls the root of the tongue upwards and back- 

 wards ; the two hyo-glossi act with these, pulling the tongue 

 backwards and downwards. The action of these four muscles 

 resembles that of a force-pump projecting the mass of fluid down 

 into the oesophagus ; it reaches the cardiac orifice with great 

 speed, and the pharyngeal and oesophageal muscles do not contract 

 on it at all, but are inhibited during the passage of the fluid 

 through them. 



This is proved in a striking way in cases of poisoning by 

 corrosive substances like oil of vitriol ; the mouth and tongue are 

 scarred and burnt, but the pharynx and oesophagus escape serious 

 injury, so rapidly does the fluid pass along them ; the cardiac 

 iiritice of the stomach is the next place to show the effects of the 

 corrosive. 



There is, however, no hard-and-fast line between the swallowing 

 of solids and fluids : the more liquid the food is, the more does 

 the force-pump action just described manifest itself. 



MOVEMENTS OP THE STOMACH. 



The gastric fluid is assisted in accomplishing its share in 

 digestion by the movements of the stomach. In granivorous 

 birds, for example, the contraction of the strong muscular gizzard 

 affords a necessary aid to digestion, by grinding and triturating 



