Physiological Morphology 99 



been given. If my interpretation of the method of growth 

 were correct, I must expect that during activity substances are 

 formed in the muscle, which determine a higher osmotic pressure 

 than those from which they originate. This is exactly the case. 

 Ranke had already shown that the blood of a tetanized frog 

 loses water and that this water is taken up by the muscles. 

 In experiments which were carried on by Miss E. Cooke in my 

 laboratory, we were able to show directly that during activity 

 the osmotic pressure inside the cell-wall is raised. We deter- 

 mined the concentration of a solution of NaCl, or rather of 

 a so-called Ringer's mixture, in which the gastroconemius of a 

 frog neither lost nor took up water. We found that while 

 this concentration for the resting gastroconemius was about 

 0.75 per cent to 0.85 per cent, for the gastroconemius that 

 had been tetanized from twenty to forty minutes it varied from 

 1 . 2 per cent to 1 , 5 per cent.' 



This increase of osmotic pressure inside the muscle-cell leads, 

 during normal activity, to a taking up of water from the blood 

 and lymph, and the consequence is an increase in volume. The 

 same muscle, as soon as it ceases to be active, begins to decrease 

 in size. Activity, therefore, plays the same role in the growth of 

 a muscle that the temperature plays in the growth of the seed. 



I tried to ascertain whether segmentation, like growth in 

 general, is influenced by the amount of water contained in the 

 cell. If we decrease the amount of water in the egg of the 

 sea-urchin segmentation is retarded, and if we use a sufficiently 

 high consentration of sea-water it may be stopped entirely. 

 Therefore the amount of water contained in the cell plays still 

 another role in the process of organization and influences the 

 process of cell-division. 



' This Increase in osmotic pressure is probably caused by the formation ot 

 acid. Two years after the pubUcation ol this lecture 1 showed that the muscle 

 swells in an isomotlc solution if this solution is acid. The recent work of Paul! 

 and Handovski indicates that the swelling is caused through a formation ol salt 

 between the acid and a weak base, e.g., a protein. The protein salt is more 

 strongly dissociated than the protein base (1912). 



