I9 o S j ' ON INTESTINAL ORGANISMS. 53 



by that of " oligodynamische " derived apparently from two Greek 

 words meaning the force within a small quantity of substance. 1 



There seems to be some confusion among recent writers as to 

 the condition of the copper produced by placing copper foil in 

 water, and it is customary to speak of the solution as being a solu- 

 tion of colloidal copper. While it has been customary since the 

 classical experiments of Graham to apply the name colloid to those 

 substances which in solution or suspension will not pass through 

 animal membranes, still recent researches have shown as pointed 

 out by Noyes 3 that there are two subclasses of colloidal mixtures, — 

 the one having the characteristic properties of true solutions, that 

 is, possessing osmotic pressure, diffusibility and usually a limited 

 solubility at some temperature ; the other being without these prop- 

 erties and being in the nature of macroscopic and microscopic sus- 

 pensions. Considering the origin of the copper in solution it would 

 properly belong to the class of colloidal suspensions, but it has none 

 of the properties of this class of substances ; and it differs funda- 

 mentally from the so-called colloidal solutions not only in origin 

 but in that it possesses the property of permeating colloids, as the 

 cell wall and the organized contents of the cell, thereby producing 

 marked disturbances in the cell and thus resembling the crystalloids. 



It is well known as stated by Copeland .and Kahlenberg 2 (page 

 455) that "every metal in contact with water and air is subject to 

 some change. It reacts with oxygen and carbonic acid dissolved 

 in water, or with the water itself, to form oxides, hydroxides, car- 

 bonates, basic carbonates, or acids, which in greater or less degree 

 pass into solution. When this chemical action is sufficient for the 

 effect to become visible, the metal is tarnished or corroded ; and 

 even gold and platinum lose their lustre." Nageli in his paper 

 (page 24) says that a solution of copper manifesting oligodynamic 

 properties results only when copper is placed in water containing 

 oxygen and carbon dioxide ; but so far no one has determined 

 which compound, or compounds, of copper is formed under these 

 conditions. 



1 As further indicating the meaning that Nageli had in mind we quote from his 

 paper (page 8) as follows : " Ich will nun, um eine bestimmte und feste Bezeich- 

 nung zu haben, die specifische Wirkungen des Giftes die chemischen, die jenigen 

 der noch unbekannten Ursache, in dem ich dem Endresultat vorgreife, die oligo- 

 dynamischen nennen." 



