98 INFECTIONS OF THE DIGESTIVE TRACT 



is connected with the inspissation of the contents of this 

 part of the tract. In some lower animals and in some 

 human individuals the desiccation of intestinal contents 

 reaches so high a grade that the fseces voided contain 

 only a very low per cent, of water. By means of this 

 absorption of moisture the organism is protected against 

 a loss of water which under certain conditions might 

 prove a detrimental condition in the struggle for existence. 

 It is easily conceivable that under primitive conditions 

 of life, where water is not always readily obtainable, 

 those animals which were best able to conserve their 

 water and salts would have a material advantage over 

 animals less well able to prevent this waste. In many 

 mammals urine of very low specific gravity is excreted, 

 although in the glomeruli of the kidneys in these same 

 animals the concentration of the urine is extremely 

 high. If it were not for the powerful resorptive action 

 of the epithelia of the convoluted and other tubules of 

 the kidney, the organism would be subjected to an 

 enormous loss of water. Under conditions where 

 water is freely obtainable such a loss would, perhaps, 

 have little significance, bu,t where the water supply is 

 uncertain such wastefulness on the part of the organism 

 would soon lead to death. Thus in the large intestine as 

 well as in the tubules of the kidney we have to recognize 

 mechanisms protective to the life of the individual 

 through provision against the waste of water. In the case 

 of man this function is of relatively little significance 

 at the present time since water may usually be obtained 

 in abundance. It seems probable that in addition to the 



