378 CHARACTERS OF THE FJ5CES. 



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 170 grms. (60-250 grms.) in 24 

 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 on water. 



The consistence of the faeces depends on the amount of water pre- 

 sent it is 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 this effect, 

 that the more energetic it 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, after section of the 

 nerves, leads to a watery condition of the faeces (p. 371). 



The reaction is often acid in consequence of lactic acid being 

 developed from the carbo-hydrates 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. 



The odour, which is stronger after a flesh diet than after a vegetable 

 diet, is caused by some faecal products of putrefaction, which have not 

 yet been isolated; also by volatile fatty acids and by sulphuretted 

 hydrogen, when it is present. 



The colour of the faeces depends upon the amount of altered bile- 

 pigments mixed with them, whereby a bright yellow to a dark-brown 

 colour is obtained. 



The colour of the food is also of importance. If much blood be present in the 

 food, the faeces are almost brownish-black from haematin ; green vegetables = 

 brownish green from chlorophyll ; bones (dog) = white from the amount of lime ; 

 preparations of iron = black from the formation of sulphide of iron. [The 

 pigment of claret tinges the fasces.] 



The faeces contain 



(1.) The unchanged residue of animal or vegetable tissues used as 

 food ; hairs, horny and elastic tissues ; most of the cellulose, woody 

 fibres, spiral vessels of vegetable cells, gum. 



(2.) Portions of digestible substances, especially when these have 

 been taken in too large amount, or when they have not been sufficiently 



