472 



DIGESTION 



about twelve minutes, being shorter than when the contractions are power- 

 ful, in which case the periods are always initiated by weaker contrac- 

 tions with long intervening pauses. Finally, the pauses disappear and 

 the contractions become more and more pronounced until, as above men- 

 tioned, a virtual tetanus, lasting from two to five minutes, may super- 

 vene. The duration of the hunger period varies from one-half to one and 

 a half hours, with an average of from thirty to forty-five minutes, and 

 the number of individual contractions in a period varies from twenty to 

 seventy. Between the hunger periods, intervals of from one-half to 

 tAvo and one-half hours of quiescence may supervene. (See Fig. 168.) 



Similar contractions, often passing into incomplete tetanus, have been 

 observed in the stomach of healthy infants, some of the observations hav- 

 ing been made before the first nursing. The intervals of motor quies- 



Fig. 166. Diagram of method for recording stomach movements. B, rubber balloon in stomach. 

 D, kymograph. F, cork float with recording flag. M, manometer. L, manometer fluid (bromo- 

 form, chloroform, or water). R, rubber tube connecting balloon with manometer. S, stomach. 

 T, side tube for inflation of stomach balloon. (From Carlson.) 



cence between the hunger periods are shorter than in adults. In obser- 

 vations made during sleep, it was observed that, when the contractions 

 were very vigorous, the infant would show signs of restlessness and 

 might awake and cry. As in the adult, the contractions are evidently 

 associated with subjective sensations of hunger. Contractions , of the 

 empty stomach have also been recorded on a large variety of animals, 

 including the dog, rabbit, cat, guinea pig, bird, frog and turtle. They 

 vary somewhat in type in different animals. 



. With regard to the time of onset of the tonus and hunger contractions, 

 it has been observed that the only period during which the fundus is 

 free of them is immediately after a large meal. After a moderate meal 

 the tonus rhythm begins to appear in about thirty minutes. It gradually 



