vi INTESTINE AS AN ORGAN OF EXCRETION 351 



exceeds that of the metabolites from the intestinal canal. But 

 with a diet consisting strictly of meat and eggs (according to 

 Rubner's experiments on man) 13-17 grins, dry faeces are ob- 

 tained, with only 0'6-1'2 grrns. nitrogen. It is therefore highly 

 probable that human faeces, like the dog's, consist mainly of 

 metabolites from the alimentary canal. 



A vegetable diet, particularly of vegetables and black bread, 

 increases the amount of faeces, with reduction of the percentage 

 quantity of nitrogen and rise of the absolute quantity. In fact, 

 (according to Rubner) the faeces for one day contain 2'4-4'3 

 grnis. nitrogen. 



Even during an absolute fast, a considerable amount of faecal 

 matter is formed in man, as shown by the interesting researches 

 of Fr. Miiller on the fasting men Cetti and Breithaupt, as well as 

 by our own observations on Succi during his fasts. The amount 

 of faeces in fasting is, however, considerably less for man than that 

 found by Voit for dogs and cats. Cetti during a fast of 10 days 

 excreted about 38 grms. faeces (when dried), i.e. 38 grrns. per 

 diem: Breithaupt in 6 days' fast excreted only 12 grms. i.e. 2 

 grms. per diem ; Succi in 30 days' fast excreted 150 grms., which 

 corresponds approximately to 5 grms. per diem, a figure somewhat 

 higher than the preceding, because Succi frequently took mineral 

 waters while fasting. 



Human faeces in fasting are yellowish-brown balls, of medium 

 consistency, with little odour, and resemble the faeces in a diet 

 consisting mainly of flesh. 



The percentage nitrogen content of the faeces in fasting is 

 greater than while taking food. In Cetti it reached S'28 per cent, 

 in Breithaupt 5 '67 per cent : while on an exclusively milk diet it 

 is 3'03-3-3 per cent ; with milk and white bread 3'92 per cent 

 (Fr. Miiller) ; with meat and bread 3*l-3'5 per cent (Meyer). It 

 is only on a strict flesh diet that we find G'5-6'9 per cent nitrogen 

 (Rubner), a figure approximately equal to the nitrogen content of 

 the faeces in fasting. Since the daily excretion of faeces is very 

 small in fasting, it follows that the absolute quantity of nitrogen 

 excreted is less than with the various diets. 



As regards the value of these observations it should be noted 

 that (according to Zaitschek, 1903, in Tangi's laboratory) the 

 ordinary method of determining the nitrogen of desiccated faeces 

 is defective, since a by no means indifferent amount of volatile 

 nitrogen is lost in the process of desiccation. The amount of 

 nitrogen which may be lost in this way varies in man from 4-7 per 

 cent, and may amount in the dog to 13 per cent. 



These analytical researches ought, therefore, to be repeated with 

 samples of non-desiccated faeces, or at least the figures quoted 

 should be revised, since they were mostly obtained from previously 

 dried faeces. 



