624 PHYSIOLOGICAL CHEMISTRY 



38. Fat in Feces. A normal adult will digest and absorb at least 

 90 per cent of the fat in the diet when the amount ingested does not 

 exceed 100 grams. If the diet contains an excessive amount of fat, 

 e.g., 300 grams per day, considerable appears in the feces. In pancreatic 

 diseases and such conditions as are accompanied by a decrease in bile 

 flow the digestion and assimilation of fat is lessened. 



Experiments. (a) Ingest an ordinary mixed diet containing an average amount 

 of fat per day, e.g., 75-100 grams. Collect a stool and examine it microscopically 

 as directed in Chapter XIV. (b) Now ingest a diet containing an excessive 

 quantity of fat, e.g., 300 grams per day. Separate the feces and subject a 

 representative sample of the feces from the high fat diet to microscopical ex- 

 amination, (c) If it is desired the fat may be extracted from some of the stool 

 by applying the principle involved in the quantitative determination of fat in the 

 Saxon method (see Chapter XIV). Evaporate the ether extract and identify the 

 fat in the residue by tests given in Chapter IX. 



39. Carbohydrate in Feces. Under normal conditions the great 

 bulk of the soluble carbohydrate in the food is absorbed from the intes- 

 tine even when the ingestion is high. Hence the content of soluble 

 carbohydrate in feces is low. To demonstrate this proceed as follows: 



(a) Ingest for three days an ordinary mixed diet to which 100 grams of glucose 

 or sucrose is daily added. Separate and preserve the feces (see page 620) and 

 when the final "marker" appears extract an aliquot portion of the total mixed feces 1 

 with water, decolorize with boneblack, filter, and after making the filtrate up to 

 a known volume determine the sugar by Benedict's method (see page 538). 

 Calculate the soluble carbohydrate content of the feces for the three-day interval, 

 (b) Proceed as above with the exception that at least 250 grams of sugar should 

 be added to the diet instead of 100 as in (a). 



How did the daily excretion of soluble carbohydrate in (a) compare with that 

 in (b)? Why is this so? If a diet of known carbohydrate content is fed this 

 experiment will give us accurate data as to soluble carbohydrate utilization (see 

 Protein Utilization, page 623). If it is desired this experiment may be combined 

 with the hyperglycemia and glycosuria experiments on pages 598 and 60 1. See 

 also Experiment 43, page 626. 



40. Inorganic Elements in the Feces. The salts of sodium and 

 potassium being very soluble are almost completely absorbed from the 

 intestine. The same is true of the chlorides including that of sodium 

 which is of greatest importance. Hence the alkali metals and chlorides 

 are excreted mainly in the urine and are found only in very small 

 amounts in the feces even when large amounts are ingested. With 

 calcium, magnesium, iron and phosphate conditions are different. Not 

 only are salts of calcium, magnesium and iron less readily absorbed but 

 they are excreted to a large extent by way of the intestinal mucosa rather 

 than by the kidneys. Ordinarily about 90 per cent of ingested calcium is 



*If time permits it is more satisfactory to analyze each individual stool in fresh 

 condition. 



