496 ABSORPTION. 



gravity of from 1*050 to 1*060, and contains salts and albu- 

 men, substances possessing highly endosmotic properties. 

 . Circulation of the blood is the most important condition 

 modifying the opposing influence of pressure. This condi- 

 tion is so important in modifying endosmosis that it de- 

 mands special consideration. It is sufficient in this connec- 

 tion, however, to appreciate the fact of its powerful influence 

 in promoting the endosmotic current. 



Variations in the pressure in the blood-vessels has already 

 been alluded to as exerting an important influence on the 

 rapidity of absorption. When the entire quantity of blood 

 is diminished by hemorrhage or prolonged abstinence, the 

 .activity of endosmosis is immensely increased ; and it is cor- 

 respondingly diminished when the pressure is increased, as in 

 plethora or after injection of fluids into the blood-vessels of 

 a living animal. This rule does not apply to those instances 

 of local increase in the pressure of blood which are attended 

 with very great increase in the activity of the circulation, as 

 in the mucous membrane of the intestinal canal during diges- 

 tion and absorption. 



In physical experiments, all observers have noticed a great 

 increase in the activity of the currents with an increase in 

 the density of the endosmotic solution. Graham found that 

 with a solution containing two per cent, of sulphate of mag- 

 nesia, the minimum of elevation in the tube of the endos- 

 mometer was 30, and the maximum 33 millimeters ; with so- 

 lutions containing five per cent, of the salt, the minimum 

 was 73, and the maximum 76 ; with solutions containing ten 

 per cent., the minimum was 134, and the maximum 152 ; and 

 with solutions containing twenty per cent., the minimum was 

 238, and the maximum 283. 1 



These facts are directly applicable to the blood and the 

 influence of the concentration of this fluid upon absorption. 



1 GRAHAM, op. cit. Philosophical Transactions, London, 1854, p. 199. These 

 figures are selected from a large number of observations upon different saline so- 

 lutions, all of which were followed by essentially the same results. 



