ACTION OF THE LARGE INTESTINE. 617 



denum. M. Blondlot, 1 however, states, that in many herbivorous ani- 

 mals and granivorous birds, as sheep, goats, pigeons and chickens, the 

 contents of the caecum were never acid unless sugar in some form had 

 been mixed with their food. The acidity of the caecum which then 

 ensues, he thinks is the result of that part of the starch or sugar, which 

 has not been absorbed in the small intestine, being transformed into 

 lactic acid. The fact of the separation of chyle in the caecum and 

 colon is proved by the experiments of M. Voisin, 2 which consisted in 

 introducing food into these intestines after the ileo-caecal valve had 

 been closed by ligature. 



The physical characters of the faeces have been already described. 

 When extruded, they have the shape of the large intestine, or of the 

 aperture, through which they have been evacuated. If the form of 

 either of these be modified, that of the excrement will be so likewise. 

 In stricture of the colon especially about the sigmoid flexure and of 

 the rectum, the faeces are squeezed through the narrowed portions, and 

 often evacuated in the shape of ribands. The quantity must, of course, 

 vary according to circumstances, and cannot be rigidly estimated. Ap- 

 proximately, they have been presumed to be, in the adult male, from a 

 quarter to half a pound in the twenty-four hours, the evacuation being 

 usually made once only in this time. The biliary secretion appears to 

 modify the appearance of the faeces greatly. If, as in jaundice, it be 

 prevented from flowing into the intestine, they are clay-coloured. M. 

 Adelon 3 affirms, that, under such circumstances, they are more fre- 

 quent. This is not the result of our experience, nor does it appear to 

 be deduced from his own ; as, a few pages before, he remarks, "it is 

 certain, that if the bile does not flow, the excrements are dry, devoid of 

 colour, and there is constipation." On the other hand, if the bile flows 

 in too great quantity the faeces are darker coloured. It is doubtful, 

 whether the varying quantity of the biliary secretion have much influ- 

 ence on the number of evacuations, unless the canal, through which it 

 has to pass, is in a morbid condition. Many of the appearances in the 

 faeces, which are conceived to be owing to a morbid condition of the 

 biliary secretion, are the effect of admixture with products of morbid 

 changes in the stomach or intestines. In elucidation of this, it maybe 

 observed, that the green evacuations of children are often referred to 

 some pathological condition of the biliary secretion ; whereas the colour 

 is commonly owing to unusual formation of acid in the stomach, the 

 admixture of which with healthy bile produces the colour in question. 



The chemical properties of the faeces have been repeatedly inquired 

 into. They must, of course, vary according to the nature of the food, 

 its quantity, the kind of digestion, &c. Human faeces were examined 

 by Eawitz 4 after animal and vegetable food had been taken. But few 

 fragments of muscular tissue were met with; but the cells of cartilage 

 and fibre-cartilage excepting those of fish were found unchanged. 

 Elastic fibres and fatty matters, which had escaped absorption, appeared 



1 Traite Analytique de la Digestion, Paris, 1844. 



2 Nouvol Aperu sur la Physiologie du Foie, &c., Paris, 1833. 3 Op. citat. 



4 Ueber die Einfachen Nahrungsrnittel, Breslau, 1846, cited by Kirkes and Paget, Manual 

 of Physiology, Amer. edit., p. 176, Philad., 1849. 



