Physiological Efficiency of Acids 145 



Why is it that, though the strong mineral acids do occasion- 

 ally work, as a rule they fail ? It has already been mentioned 

 that if they produce any effect, membrane formation does 

 not set in while the eggs are in the acid solution, but only after 

 they have been transferred to normal sea-water. It is possible 

 that the mineral acids only cause membrane formation indi- 

 rectly, their immediate effect being to liberate from its salts 

 some fatty acid contained in the surface of the egg, and that 

 then the fatty acid thus liberated instigates membrane forma- 

 tion. This hypothesis is supported by the following obser- 

 vation. If 2 or 3 c.c. of N/10 HCl are added to 50 c.c. of 

 sea-water, and unfertilized eggs placed in this solution, no 

 membranes are as a rule formed by the eggs after transference 

 to normal sea-water. A similar result is obtained if, instead of 

 HCl, 2 or 3 c.c. of N/2 sodium butyrate are added to the sea- 

 water. But if both HCl and sodiiun butyrate are added simul- 

 taneously to the sea-water, the eggs do form a membrane 

 when transferred from this to normal sea-water. In this case 

 butyric acid is produced and diffuses into the egg. And there 

 is no reason for supposing that a similar reaction may not ,take 

 place when HCl comes into contact with the surface of the egg; 

 for it might liberate here one of the higher fatty acids contained 

 in combination in the surface of the egg. 



It may also be mentioned that the addition of a slightly 

 effective mineral acid, such as HCl, to butyric acid does not 

 influence the activity of the latter. I have performed many 

 experiments of the kind, to see how far HCl can replace the 

 fatty acid. It appears that HCl can only enter as substitute 

 for a small amount of the fatty acid; perhaps some acid is 

 combined with the proteins of the egg (especially of the chorion), 

 and only this amount of fatty acid can be replaced by HCl. 

 If more is added, everything proceeds as though the fatty acid 

 concerned were in solution alone. The only effect of the sur- 

 plus of H ions is that the confluence of the drops in membrane 



