352 PHYSIOLOGY CHAP. 



The faeces of fasting contain a certain amount of fat, which is 

 probably eliminated with the intestinal secretions. 



It is interesting in this connection to note that U. Lombroso 

 observed in some cases, after excising the pancreas in dogs, that 

 more fat was given off in the faeces than had been present in 

 the food, and again that fat was eliminated in large quantities 

 with a diet of egg -albumin (which contains only traces of fat). 

 This shows that under certain conditions the elimination of fat 

 by intestinal excretion may far exceed the limits generally 

 acknowledged. 



It has further been observed that during a diet rich in fats 

 the faecal fat exhibits a much higher melting-point than the 

 alimentary fat. With a milk diet (milk-fat melts at 42) a fat 

 is found in the faeces which melts at 51'5 (Miiller, Zoja). 



This has been explained by a selective capacity of the intestinal 

 epithelium during fat absorption ; in the sense that the epithelium 

 has the capacity of absorbing specific fats which vary according to 

 the species of animal This hypothesis, however, does not agree 

 with the fact that on feeding previously emaciated animals on 

 special fats other than that of their bodies (olive oil, mutton suet) 

 these are found unchanged in the adipose tissues. It is therefore 

 not improbable that selective activity is to be referred not so much 

 to absorption as to the elimination of such fatty bodies as are not 

 easily assimilated by the tissues of the animals of the particular 

 species. 



The ash of the faeces during a fast does not differ in amount 

 from that with a normal diet. It differs in composition from the 

 ash of the meconium in having less sulphuric acid, chlorine, and 

 alkali, and more phosphoric acid and calcium. In the faeces of a 

 mixed normal diet these last substances are present in a higher 

 quantity than in fasting. 



III. Hermann (1890) employed quite a different method to 

 determine the importance of the intestinal mucous membrane in 

 the formation of the faeces. He isolated a loop of intestine in the 

 dog, washed out its contents by a stream of disinfecting fluid, 

 sutured the ends to form a ring within which the substances 

 introduced could circulate, and then replaced it in the abdominal 

 cavity, which was closed up, after renewing the continuity of the 

 rest of the gut by a second suture. 



Many animals thus operated on died after a few days from 

 septic peritonitis, owing to the escape of faecal matters through 

 the suture of the circular loop of intestine. Some dogs, however, 

 survived for a long time, and were killed in the 3rd-4th week after 

 the operation in a good state of health. Upon section, the ring 

 was found to be filled with a grey mass of faecal matter, which 

 differed from the normal faeces only in the absence of bile and of 

 alimentary residues. According to Hermann, this more or less 



