468 Prof. Liebig on the Constitution of 



the fluid within the channels of circulation, i. e. the blood, and 

 the fluid without these vessels, i. c. the saline water, not exer- 

 cising any physical action upon one another, /. e. not inter- 

 mixing by endosmose or exosmose. 



Water containing a larger amount of salts than the blood, 

 such as common sea-water, for instance, and even the weaker 

 kinds of saline mineral waters, exercise again a different action 

 from that of pump-water mixed with I'lOOth of common salt; 

 not only no emission of urine takes place after the imbibition 

 of such saline water, but water exudes from the circulating 

 vessels into the intestinal canal, and, together with the saline 

 solution, is carried off through the rectum ; purgation takes 

 place, attended with much thirst, if the saline solution be in 

 some measure concentrated. 



Considering that a certain amount of salts is absolutely ne- 

 cessary to constitute normal blood, we may deduce from these 

 observations and experiments (which any one may easily imi- 

 tate and verify upon his own person) that the physical condi- 

 tion of the tissues or of the blood-vessels opposes an obstacle 

 to any increase or decrease of the amount of salts in the blood ; 

 and thus that the blood cannot become richer or poorer in 

 salts beyond a certain limit. 



Fluids containing a larger amount of salts than the blood 

 remain unabsorbed, and leave the organism through the rec- 

 tum; fluids containing a smaller amount of salts than the 

 blood enter into the circulation, absorb, and remove from the 

 organism, through the urinary channels, all the soluble salts 

 and other substances which do not belong to the constitution 

 of the blood ; so that, finally, only those substances remain in 

 the organism which exist in chemical combination with the 

 constituents of the blood, and which, therefore, are incapable 

 of being secreted by the healthy kidneys. 



I have convinced myself, by careful and minute examina- 

 tions, that urine emitted after drinking a copious amount of 

 water invariably contains a somewhat larger amount of salts 

 than the water which has been drunk ; whilst the amount of 

 phosphates contained in the last emitted portions of the urine 

 is extremely minute, and no longer detectable by the ordinary 

 tests. It is therefore obvious that all the salts, without ex- 

 ception, contained in the urine, are to be considered as acci- 

 dental constituents of the blood, which are excreted and re- 

 moved from the organism precisely because they no longer 

 form part of the normal constitution of the blood. The piios- 

 phates emitted with the urine were, previously, constituents of 

 substances which have been decomposed in the vital processes, 

 or they existed as constituents of the blood, but upon its trans- 



