196 TEXT-BOOK OF PHYSIOLOGY. 



ate about a pound and a half of beef-heart daily, but always refused fat. 

 There was an absence at all times of jaundice, fetor of the breath, and fall- 

 ing of the hair. Post-mortem examination showed that the bile-duct was 

 obliterated, and there was no evidence that any bile could have passed into 

 the intestine. The results of this and similar cases go to show that that por- 

 tion of the bile which is secretory in character is essential to digestion and 

 the nutrition of the body that, though large quantities of food are con- 

 sumed, progressive diminution of weight takes place until nearly 40 per 

 cent, of the body is consumed. In some instances the breath becomes 

 fetid and there is a falling of the hair, showing some profound disturbance 

 of the general nutritive process. 



The Movements of the Small Intestine. The movements of the small 

 intestine have been studied by means of the Rontgen rays by Cannon. The 

 method adopted was to mix with the food subnitrate of bismuth, which being 

 opaque rendered the movements of the intestinal contents and thereby the 

 movements of the intestinal walls visible on the fluorescent screen. There 

 investigations revealed the presence of two forms of activity, one of which is 

 more or less stationary and due to rhythmic contraction of circular muscle- 

 fibers, the other progressive, passing from above downward and due to the 

 contraction of circular and longitudinal muscle-fibers. The former activity, 

 which is by far the more common, results in a division of the intes- 

 tinal contents into small segments and for this reason was termed by Can- 

 non rhythmic segmentation; the latter activity is the well-known peristaltic 

 wave. 



Rhythmic Segmentation. When the abdominal cavity is investigated by 

 the method above mentioned, it is observed that after the food has passed 

 into the intestine and formed a more or less consistent mass of variable 

 length, bands of circular muscle-fibers, situated at regular distances one 

 from another, begin to contract and divide a mass of food into segments, 

 after which they at once relax to be followed by contraction of other bands in 

 the segments of the intestines overlying the segments of food. The result is 

 again a division of the food into two new segments (Fig. 85). The lower 

 half of each segment then unites with the upper half of the segment of food 

 below to commingle with it and expose new surfaces of the food mass to 

 contact with the actively absorbing mucosa. The continual repetition of 

 this process results in a thorough mixing of the food with the digestive juices. 

 From the manner in which these contractions make their appearance it would 

 seem that the mere presence of a segment of food in the lumen of the intestine 

 is sufficient to excite the overlying fibers to activity. 



In certain regions of the intestine rhythmic segmentation may continue 

 for half to three-quarters of an hour without moving the food forward to any 

 marked extent. In the cat the segmentation may proceed at the rate of 

 thirty divisions a minute. 



Peristalsis. After the food has been prepared by the process described 

 in the foregoing paragraph, it is then slowly carried downward by what is 

 known as the vermicular or peristaltic wave. This wave is characterized by 

 a contraction of the circular fibers behind the mass of food and a relaxation 

 of the fibers in advance of it. The result is a movement forward of the food, 

 and as it moves it is followed by a ring of constriction and preceded by a 



