55 



rate of growth does not depend upon the presence of 

 growth promoting sul)stances onh% but also upon the cou- 

 centrations of various substances, the osmotic pressure, sur- 

 face tension and many other physico-chemical factors. The 

 technique and some of llie experiments will be described 

 in detaii, because this method is found to be most preserving 

 for the delicate substances, and will certainly contribute to 

 the understanding of the nature of the growth promoting 

 substances in the body juices. 



Besides a number of i)reliminary experiments, w^here 

 proper amount of adsorbent to be used was found, all the 

 experiments were made under the control of the hydrogen 

 ion concentration. 



The recent investigations of Loeb ^ti) on amphoteric col- 

 loids has shown what an important and determining factor 

 the hydrogen ion concentration is for the process of adsorp- 

 tion or more correctly, the chemical binding. As we have 

 no idea of the chemical nature of the growth })romoting 

 substances, and we do not know the hydrogen ion con- 

 centration by which we shall obtain unition with the adsor- 

 bent, it was therefore necessary to know a little about 

 the character of the adsorbing materials. The different ad- 

 sorbents were then investigated by means of cataphoresis 

 experiments to find out their respective iso-electric points. 

 According to the electrical charges of the dissociated protein 

 bodies, the cationic and anionic aggregates will be adsorbed 

 either on the one or the other side of the iso-electric point 

 of the adsorbent; this depending only upon the hydrogen 

 ion concentration of the solution. 



Experiments were undertaken to see, at what hydrogen ion 

 concentration the adsori)tion of the growth promoting sub- 

 stances has its maximum, and furthermore to see to what 

 an extent these adsorbed substances could be displaced from 

 the adsorbent. At the same time chemical analysis were 

 made of the adsorbent including the adsorbed substances as 

 well as of the supernatant fluid. The rate of growth was 



