June 17, 1918 Physical Changes in Feed Residues in Cattle 645 



COMMINUTION IN ABOMASUM 



A more constant amount of comminution takes place in the abo- 

 masum than in the omasum, and the rations associated with the greater 

 comminution are those made up of a higher percentage of coarse feeds, 

 as in the silage alone. 



COMMINUTION IN SMAI,!, AND LARGE INTESTINES 



Owing to the nature of digestion from a physical standpoint, the early 

 part of the digestion period is consumed largely with a process of com- 

 minution and preparation, and comparatively little absorption takes 

 place. During the later stages of digestion the extent of comminution 

 is presumably much less, and absorption is much greater. The existence 

 of this condition is brought out clearly in Tables IV and V, where it 

 is seen that the extent of any comminution that takes place in the in- 

 testines is either partially or completely overshadowed by absorption. 

 Since the absorption takes place much more rapidly with those particles 

 under 2 mm. than with those over 2 mm., we obtain several negative 

 percentage comminutions. The fact that the figures obtained for the 

 intestines are composite figures representing two opposite effects, com- 

 minution and absorption, renders them of but little value in making 

 deductions, since no method is available which will enable us to deter- 

 mine the extent of either factor alone. 



re;lation .between time food remains in organs and extent op 



comminution 



A study of Tables IV to VI shows a relationship between the extent of 

 comminution, the time the food residues remain in the organs, and the 

 functional activities of the several organs. In general, the food residues 

 remain the shortest time in the most active organs and the longest time 

 in the most inactive. This is seen in the case of the abomasum, prob- 

 ably the most active organ functionally, in which food remains on the 

 average only 2.83 hours, while in the rumen and reticulum, probably the 

 most inactive functionally of all the organs, in which the food remains 

 on the average over 60 hours, we find the extent of comminution not to be 

 in proportion to the time. F'rom a study of the figures it is seen that the 

 extent of comminution is a resultant of two forces, time and functional 

 activity, the functional activity being the stronger of the two influences. 

 Thus, even though the food mass remain in the omasum for approxi- 

 mately three times as long as in the abomasum, the extent of comminution 

 is about the same in both organs, the greater functional activity of the 

 abomasum replacing the time factor in the omasum. As previously 

 noted, the extent of comminution in the intestines is confused by absorp- 

 tion, so that no studies can be made on these data with reference to these 

 relationships. 



