CHAPTER I. VII 

 BACTERIAL DIGESTION IV THE [NTESTINE 



On an average diet, in twenty-four hours the feces of man weigh 

 about 100 grams, or niter drying, aboul 20 grams. Aboul one-fourth of 

 t ho dry matter consists of the bodies of bacteria, h' plated out by I 

 ordinary bacteriologic methods, however, it will be found that only a 

 small proportion of these bacteria are Living. The greater Dumber have 

 been destroyed, probably by the action of the mucin in the large inl 

 tine. The nitrogen contenl of the feces amounts to aboul 1 5 gran 

 day, of which aboul one-half is bacterial nitrogen. It" the did ains 



large quantities of cellulose material, as in green vegetable food and 

 fruit, the mass of feces as well as the bacterial contenl may be 

 erably greater. 



The foregoing fads indicate that very extensive bacteriologic pr 

 esses must be going on all the time in the intestinal contents, and the 

 question arises as to whether such action is beneficial or otherwise to the 

 animal economy. To answer this question interesting observations have 

 been made on the growth and well-being of animals excised from the 

 uterus under strictly sterile conditions and maintained then 

 sterile food. Such observations made on guinea pigs have shown that 

 the animals thrive and grow perfectly for a considerable time. Experi- 

 ments carried out on chicks have not, however, yielded similar results, 

 ('hicks hatched oul from the egg under strictly sterile conditions and 

 then fed on sterile grain, do not thrive, but do so if with the '-'rain is 

 mixed a certain amounl of fowl excrement. These experiments, appar- 

 ently contradictory in their results, show that \'<<v certain groups of 

 animals bacteria are required, bul QOl for Oth( 



The difference Is probably dependenl on the nature of the foods. It 

 will be remembered thai the size of the large intestine varies consider- 

 ably according to the nature of the diet a page 163 Ai i als taking 

 great quantities of cellulose foodstuffs have very large ceca and v< 

 long large intestines; whereas those which, like tl I ally 



entirely on cellulose-free food, have a rudimentary large intestine. The 

 of the lower intestine is obviously dependenl on the p' 



absence of cellulose in the food. It will be remembered also that the 



forward movement of the contents of the large intestine is very slow : 



ind 1. special provision is made, by the present I tl ftnti- 



