EXPERIMENT STATION BULLETINS. 225 



starch of the food into a kind of sugar. In the stomach the gastric 

 juice converts part of the ])rotein into a soluble form. In the stomach 

 too part of the sugar may be absorbed and go directly into the circuhi- 

 tion. 



From the stomach the food passes into the small intestines. Here, 

 after i)assing along a few inches from the stomach it is mixed with bile 

 which conies through th(> bile duct fi"om the liver. The contents of the 

 stomach are acid, the bile is distinctly alkaline. Along with the bile, 

 though discharged into the intestines through a difTerent tube, comes a 

 juice, perhaps the most important in its functions of any of the diges- 

 tive fluids. This is called the pancreatic juice, a secretion of the 

 pancreas. 



It is the function of the bile to act ui)on the fats in such a way as to 

 fit them to be absorbed. Just how it accomplishes this end is not 

 fully known. Possibly it emu Isi ties them, that is, divides them into 

 minute particles which are held in suspension and which may be 

 absorbed. Next, the bile seems to exert an antiseptic inllucnce on 'the 

 contents of the intestines i)reventing decay. Third, the bile acts as a 

 partial lubricant. Fourth, it prepares the ])artly digested food for the 

 action of the j)aTn'reatic Juice. Among the functions of the latter fluid 

 possibly the most important, is the digestion of tlu> protein. It con- 

 verts tlie protein bodies into simpler compounds which are soluble and 

 therefore capable of absorption. Next it transforms starch into sugar 

 and other soluble bodies. Third, it breaks up the fats into glycerine 

 and fatty acids. 



There are other juices secreted by the walls of the intestines. They 

 aid in digestion largely by converting the carbohydrates into a form of 

 sugar in which form they are absorbed. The whole aim of digestion is to 

 make soluble the food materials eaten. They are therefore* grouiul by 

 the teeth, then soaked in a succession of acid and alkaline licpiids that, 

 cond)ined, act u])on all of the food elements, rendering them soluble. 



Notwithstanding the elaborate ecpiipment for digestion furnished by 

 nature, it must needs be that i)art of the protein, carbohydrates and 

 fat taken in the mouth in the form of hay and grain, must escape diges- 

 tion. As a matter of fact little more than half of some of the valuable 

 nutrients of the forage crops are absorbed and become really useful to 

 the animal. 



It is evident that in estimating the value of a given cattle food, we 

 ought to take into consideration the digestible i)art only. The share 

 of tlie protein for instance that, under ordinary circumstances, i)asses 

 through the cow undigested, is of no value as far as she is concerned 

 and should not be counted upon in calculating the amount of material 

 she wouUl receive in her daily ration. In comparing two fo<lders, there- 

 fore, it is not enough to know how much of the total nutrients each 

 contains, we must know in addition the share that is digestible. Hav- 

 ing determined the i)ropor(ion of digestible |)rotein, carbohydrates and 

 fat in each of our fodders we will thereafter take account of those 

 digestible i)arts only. 

 29 



