

PROCESSES IN THE LARGE INTESTINE. 283 



It is of the utmost importance, in connection with the processes of putrefaction, 

 to determine whether they take place when oxygen is excluded, or not. When O 

 is absent, reductions take place ; oxy-acids are reduced to fatty acids, and H,CH 4 

 and H 2 S are formed; while the H may produce further reductions. If be 

 present, the nascent H separates the molecule of free ordinary oxygen ( = 2 ) into 

 two atoms of active oxygen ( = O). Water is formed on the one hand, while the 

 second atom of O is a powerful oxidising agent (Hoppe-Seyler). 



It is remarkable that the putrefactive processes, after the development of phenol, indol, 

 skatol, cresol, phenylpropionic and phenylacetic acids are subsequently limited, and after a 

 certain concentration is reached, they cease altogether. The putrefactive process produces 

 antiseptic substances which kill the micro-organisms, so we may assume that these substances 

 limit to a certain extent the putrefactive processes in the intestine. 



The reaction of the intestine immediately below the stomach is acid, but the 

 pancreatic and intestinal juices cause a neutral and afterwards an alkaline reaction, 

 which obtains along the whole small intestine. In the large intestine, the reaction 

 is generally acid, on account of the acid fermentation and the decomposition of 

 the ingesta and the faeces. 



185. PROCESSES IN THE LARGE INTESTINE. Within the large in- 

 testine, the fermentative and putrefactive processes are certainly more prominent 

 than the digestive processes proper, as only a very small amount of the intestinal 

 juice is found in it. The absorptive function of the large intestine is greater than 

 its secretory function, for at the beginning of the colon its contents are thin and 

 watery, but in the further course of the intestine they become more solid. Water and 

 the products of digestion in the solution are not the only substances absorbed, but 

 under certain circumstances, unchanged fluid egg-albumin, milk and its proteids, 

 flesh-juice, solution of gelatin, myosin with common salt, may also be absorbed. 

 Experiments with acid-albumin, syntonin, or blood-serum gave no result. Toxic 

 substances are certainly absorbed more rapidly than from the stomach. [In the 

 dog the secretion of the large intestine has no digestive properties, but fats are 

 absorbed in it. Klug and Koreck regard its Lieberkiihnian glands not as secreting- 

 but as absorbing-structures.] The faecal matters are formed or rather shaped in 

 the lower part of the gut. The caecum of many animals, e.g., rabbit, is of consider- 

 able size, and in it fermentation seems to occur with considerable energy, giving 

 rise to an acid-reaction. In man, the chief function of the caecum is absorption, 

 as is shown by the great number of lymphatics in its walls. From the lower part 

 of the small intestine and the caecum onwards, the ingesta assume the faecal odour. 



The amount of faeces is about [5 oz. or] 170 grms. (60 to 250 grms.) in twenty- 

 four hours; but if much indigestible food be taken, it may be as much as 

 500 grms. The amount is less, and the absolute amount of solids is less, after 

 a diet of flesh and albumin, than after a vegetable diet. The faeces are rendered 

 lighter by the evolution of gases, and hence they float in water. 



The consistence depends on the amount of water present usually about 75 per 

 cent. The amount of water depends partly on the food pure flesh diet causes 

 relatively dry faeces, while substances rich in sugar yield faeces with a relatively 

 large amount of water. The quantity of water taken has no effect upon the amount 

 of water in the faeces. But the energy of the peristalsis has. The more energetic the 

 peristalsis is, the more watery the faeces are, because sufficient time is not allowed 

 for absorption of the fluid from the ingesta. Paralysis of the blood- and lymph- 

 vessels, or section of the nerves, leads to a watery condition of the faeces ( 183). 



The reaction is often acid, in consequence of lactic acid being developed from the 

 carbohydrates of the food. Numerous other acids produced by putrefaction are 

 also present ( 184). If much ammonia be formed in the lower part of the intestine, 

 a neutral or even alkaline reaction may obtain. A copious secretion of mucus 

 favours the occurrence of a neutral reaction. 



