38ii 



tinues to fall until the period is well passed has not heen determined. 

 The effects on the breeding operations while of paramount importance 

 have not been touched in this investigation. In this work no experi- 

 ments were performed between June 8 and Aug. i8. 



In the course of the investigation the working out of the toxicity 

 of the different compounds has been rendered essential, first because 

 of their general occurrence as by-products and secondly because va- 

 rious methods of treatment remove some compounds and not others. 

 This toxicity is further of interest in connection with the effects of 

 these compounds as drugs and poisons. The recent use of gold fishes, 

 frogs, etc. as means of standardizing drugs, such as digitalis, renders 

 these data of interest to the pharmacist and legal toxicologist. The 

 timed killing of upwards of 1,500 fishes has, it is hoped, made clear 

 some facts and methods which may be useful in the study of these 

 problems wdth domesticated species such as gold fish. 



III. MateriaIv and Methods. 



The character of the water used is of much importance in the study 

 of toxicity of polluting substances. The loss of oxygen and accumula- 

 tion of waste matter in standing water renders experiments conducted 

 wdth it open to criticism and necessitates the use of a short period to 

 death in comparatively high concentrations of the drugs as a criterion 

 in determining relative toxicity. It further necessitates the running 

 of control experiments in running water. Experiments in running 

 water are usually necessary in the case of gases. Toxicity is frequent- 

 ly different in distilled water and tap water. 



I. the; character OE university of ILEINOIS WATER, AND OTHER 



W^ATER PROBLEMS. 



The water supply of the University comes from deep wells and 

 the salts are nearly all present in the form of carbonates instead of a 

 mixture of carbonates, chlorides, and sulphates as is the case in waters 

 where fish normally occur. It also contains about twice as much 

 magnesium and calcium and eight times as much iron as is commonly 

 present in such waters. As it comes from the tap the university water 

 contains no oxygen and about iScc. per liter of carbon dioxide. The 

 lack of oxygen alone makes it unsuitable for fishes, and the presence 

 of so much carbon dioxide renders it wholly unfit for them. Fishes 

 die in it quickly. The mortality among fishes brought in from streams 

 was very great when this water was used in aquaria in which they 

 were kept. 



