414 COLLOIDS IN BIOLOGY AND MEDICINE 



cent after which diarrhea occurred. If he deprived the animal of 

 water for 1 or 2 days and gave only a dry diet, even concentrated 

 solutions, of Glauber's salt (20 gm. salt) had no cathartic action. 

 The same quantity of salt diluted to a 5 per cent solution resulted in 

 strong catharsis after one or two hours. We see, therefore, that the 

 condition of the tissues and blood colloids in respect to swelling play 

 a most important part in these processes. On this account it is 

 possible to employ the salts of Group I and MgS0 4 either to purge or 

 to dehydrate the body as may be necessary. It is important to con- 

 sider how purgative action is to be measured; whether according to 

 the amount of dried substance passed or according to the total 

 quantity including the fluid. A fluid stool permits us to conclude that 

 there is an increase of secretion or a diminution of absorption, an 

 increased amount of solid feces suggests an increase of peristalsis. 



Astringents. 



Constipating substances, i.e., those which diminish the intestinal 

 or even the gastric secretion and peristalsis, are substances which 

 diminish stimuli. As such are employed, as has been mentioned on 

 page 365, hydrophile colloids (mucilages, etc.), as well as strongly 

 adsorbent suspensions (talc, bismuth subnitrate, bismuth subgallate). 

 More powerful actions are obtained with such substances which tan 

 the intestinal membrane superficially and in this way interfere with 

 the secretion of the intestinal glands, or at least arrest absorption 

 at the point affected. Most important of these is tannin and such 

 tannin compounds as are dissolved in the intestinal juice (tannalbin, 

 tannigen). 



BALNEOLOGY. 



It would certainly be a fortunate circumstance for balneology if 

 we knew but a small fraction as much about the physiological action 

 of medicinal springs as we at present know of their physical and 

 chemical properties. Every mineral spring, no matter how insignifi- 

 cant, has its chemical composition determined to the fifth decimal; its 

 osmotic pressure, conductivity, radioactivity, etc., are investigated 

 and the possibilities of its therapeutic activity are lauded and its 

 clinical successes (not the failures) are carefully registered. 



The scientifically determinable and explicable effects are con- 

 sidered by very few. From these remarks it must not be concluded 

 that valuable clinical results are not to be obtained by means of 

 balneology, but that its scientific basis is largely undetermined. 



