159] THE GOLDFISH AS A TEST ANIMAL— POWERS 39 



activity of water distilled in copper stills with block-tin leads and possibly 

 also the CuCl2, CdCl2, and FeCls solutions is probably due to the presence of 

 a colloid. This is in keeping mth Locke's (1895) results in which he showed 

 that distilled water may lose its toxic activity by long boihng, and especially 

 when brought in contact with sulphur, carbon, manganic oxide, cotton, wool, 

 silk, and other substances, and those of Wells (1915) who found distilled water 

 no more toxic than tap-water so long as the distilled water was sUghtly acid. 



