412 COLLOIDS IN BIOLOGY AND MEDICINE 



ing to H. MEYER and R. GOTTLIEB,* about 3 to 4.5 liters daily. The 

 amount reabsorbed is a still larger quantity. An increased absorp- 

 tion of fluid is followed by an increased secretion of fluid into the 

 intestine. The final result depends on whether more fluid is ab- 

 sorbed or secreted (into the intestine) or vice versa. If the secretion 

 exceeds reabsorption the intestinal contents are fluid and volumi- 

 nous, and we have one of the conditions for easy defecation. On this 

 account substances having a capacity for swelling counteract con- 

 stipation. Persons suffering from constipation are recommended to 

 eat considerable quantities of vegetables and graham bread, because 

 the indigestible cellulose they contain retains water. This accounts 

 for the laxative action of agar. In addition, all substances which act 

 on the intestinal nerves by increasing peristalsis will favor defecation. 



The effect of alkali salts have been most exhaustively investigated, 

 but before we consider them we must recall the observations of 

 LOEPER.* He found that salt solutions which were introduced orally 

 either in hypertonic or in hypotonic solution, when they reached the 

 intestine were in practically isotonic solution. We can accordingly 

 disregard all hypotheses which seek to explain the action of purgatives 

 by differences of the osmotic pressure of the intestinal contents. If 

 hypertonic or hypotonic salt solutions have an effect notwithstanding, 

 we must explain this by indirect action, for hypertonic salt solutions 

 inhibit gastric movements and thus interfere with the progress of 

 the chyme from stomach to intestine. 



We saw that the chlorids and nitrates are diuretics; the sulphates, 

 phosphates, citrates and tartrates are chiefly purgatives, so that the 

 last-mentioned anions must possess properties which either increase 

 secretion, diminish absorption, or strengthen peristalsis. 



Some diuretics may purge by reason of increased secretion. Table 

 salt acts in this way and, in mild constipation, it is given in dry 

 form in Spa cures, or as sodium bicarbonate. 1 



In the case of the real purgatives of Group I, it is a question 

 whether their action is directly on the intestinal mucous membrane 

 or whether they increase peristalsis through nerve stimulation. Pos- 

 sibly they may impede the absorption of themselves and other sub- 

 stances by dehydrating and precipitating albumin. This does occur 

 in high concentration (1 gram equivalent Na2S0 4 ). G. QUAGLIARI- 

 ELLO * has shown in the case of sodium sulphate that for such salt 

 concentrations as enter the intestine after passing through the 

 stomach, the imbibition of water is no different than for sodium 

 chlorid, and accordingly that there is no direct action by such purga- 

 tive salts on the intestinal mucous membrane. 



1 Changes into sodium chlorid with the gastric hydrochloric acid. 



