PASSAGE OF FOOD FROM MOUTH TO STOMACH 759 



rays. The subnitrate of bismuth may be mixed with milk for a 

 fluid or with bread and milk for a semi-solid substance, or may be 

 enclosed in a cachet and swallowed as a solid bolus. The time of 

 entry of the food into the stomach may be determined by auscultating 

 with a stethoscope over the region of the cardiac orifice. Since 

 a certain amount of air is. always swallowed at the same time as the 

 food, the escape of this air through the small cardiac orifice gives 

 rise to a bubbling noise which can be easily heard. In the horse 

 the movement of a bolus down the oesophagus can be seen or felt 

 from the outside of the neck. The relative time-relations of the 

 events at different parts of the oesophagus may be obtained by passing 

 sounds provided with rubber balloons to different levels in the tube 

 and connecting these sounds with recording tambours or piston 

 recorders. This method has been employed both in men and in 



animals. 



When a mouthful of water is taken two sounds may be heard 

 on auscultating over the oesophagus. The first sound immediately 

 follows the beginning of the act of swallowing and is probably due to 

 the impact of the fluid against the posterior pharyngeal wall brought 

 about by the sudden contraction of the mylohyoid and other muscles 

 which throw the fluid from the back of the tongue across the pharynx. 

 The second sound is heard best by listening over the epigastrium. 

 It begins from four to ten seconds after the first sound, and lasts 

 for two or three seconds. The interval between the two sounds is 

 not constant, and may vary in the same individual. If the observa- 

 tion be carried out on a man lying on his back, the trickling second 

 sound is changed into a series of sounds which have been described 

 as squirts, which vary from two to five in number, each lasting about 

 one second. The second sound may be absent when a solid bolus 

 is swallowed. On observing the process by Rontgen rays very 

 much the same time-relations are obtained. If a mouthful of milk 

 mixed with bismuth carbonate be swallowed, it will be seen passing 

 rapidly down the oesophagus to the cardiac orifice of the stomach. 

 Here the passage becomes slow, and the fluid escapes slowly in a 

 narrow stream into the stomach. The average time which elapses 

 between the beginning of deglutition and the disappearance of the 

 last trace of fluid from the oesophagus is about six seconds. The 

 same course of events is induced when the food swallowed is semi- 

 solid. If, however, the bolus be dry, such as a cachet of bismuth 

 carbonate, it may pass down the oesophagus with extreme slowness 

 and may take as much as fifteen minutes to reach the cardiac 

 orifice, although the individual who has swallowed it is quite unaware 

 of its continued presence in the oesophagus. If, as would normally 

 be the case, the cachet be well moistened with saliva 01 water before 



