PREFACE vii 



and their higher derivatives either pass out of the pseudo- 

 basic-pseudo-acid state, or will they be prevented from 

 entering into it. In other words, only in the presence of 

 salts will amino-acids and their higher derivatives interact. 

 A new view has been advanced, namely, that so-called neutral 

 salts are, as a matter of fact, not neutral, for it is their very want of 

 neutrality which allows them to dissolve in water, and which also 

 enables them to dissolve globulins or to keep these compounds in 

 solution. 



10. Colloids are dealt with on lines similar to those adopted in 



my book on Physiological Histology, with the inclusion of 

 certain additional matter, such as the papers of Posternak, 

 which had escaped my notice when writing my first book. 

 The more recent literature has also been added. The view 

 first advanced by me in 1902, that the action of any given 

 metal is the function of its electro-affinity, seems to have 

 received complete confirmation through Galeotti and Pauli, 

 whose researches are so important that they are given very 

 fully. The conception that colloids are electrolytes, first put 

 forward by me in my Physiological Histology, has since then 

 also been advanced in papers coming from Ostwald's and 

 Nernst's laboratories, and is once more insisted upon in this 

 book. In regard to the question of mechanical conglutination 

 or coagulation, Dr. Ramsden has been good enough to give 

 me in his own words such information as he has obtained by 

 his recent work. 



11. The study of the autodigestion of the nucleo-proteids seems 



destined in the near future to throw more light on the 

 question of metabolism than almost any other study, and 

 hence the matter has also been specially gone into. 



12. In the chapter on blood I have enjoyed the great privilege of 



extensive help by our first authority on blood, namely, Dr. 

 John Haldane, F.R.S., to whom I wish to express my sincere 

 thanks, especially as he has allowed me to make known 

 several as yet unpublished observations. 

 b 



