150 THE SECRETIONS: 



urine, in this experiment, emitted in the last evacuation, will 

 be clear and colourless, like pump-water, and the amount of 

 salts it contains is little more than is contained in pump-water. 

 There are individuals who are capable of thus imbibing from 

 six to eight quarts of water consecutively without any in- 

 convenience. 



"But the case is quite different with water possessing an 

 amount of salts equal to that of the blood ; if even as little as 

 l-100th part of common salt be added to pump-water, and from 

 three to four glasses drunk, no evacuation of urine will take 

 place, even two hours after drinking. It is almost impossible 

 to drink more than three glasses of this saline water, for it 

 weighs heavily on the stomach, as if the absorbent vessels had 

 no power of taking it up. This obviously arises from the fluid 

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

 without these vessels, i. e. the saline water, not exercising any 

 physical action upon one another, i. e. not intermixing 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 1 -100th 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 tube, 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 condition 

 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 rectum ; 

 fluids containing a smaller amount of salts than the blood enter 



