890 BULLETIN OF THE BUREAU OF FISHERIES. 



notwithstanding the fact that they, too, have been brought under domestication 

 and are subject to all the increased susceptibility to disease that is always con- 

 sequent upon this more restricted life. The difference is due in part to the 

 relative youth of the science of fish culture and the, so far, relative absence of 

 disease, and in part to the difficulty of administering medicine in the presence 

 of water, from which the fishes can not long be separated. It is obvious, how- 

 ever, that with a remedy that may be applied externally and a process for apply- 

 ing it by means of the water the fish live in, important possibilities are at hand. 

 If copper sulphate, for instance, can be shown to be toxic to the pathogenic 

 bacteria and external parasites of fishes in dilutions yet harmless to the fishes 

 themselves, it will have a much wider usefulness in fish culture than its present 

 application. The only experiments to this end so far undertaken have been 

 inconclusive, but future experiments may be expected to show useful results in 

 this field. 



TABLE OF METRIC EQUIVALENTS. 



1 centimeter = 10 niilliraeters=o.3937 inches. 



I gram =1,000 milligrams (mg.)= 15.43 grains. 



I avoirdupois ounce =28.35 grams. 

 I apothecaries' ounce= 3 1. 10 grams. 

 I avoirdupois pound=453.6 grams. 

 I fluid dram =370 cubic centimeters. 



I gallon =231 cubic inches=3, 785.4 cubic centimeters (c. c). 



I cubic inch =16.387 cubic centimeters (c. c). 



1,000 c. c. =1 liter. 



I teaspoonful =1 dram, or 3.7 c. c. 



I c. c. of pure water weighs i gram. 



Ordinary teaspoons are variable and usually hold more than 3.7 c. c. Medicine glasses graduated 

 in teaspoonfuls (drams) may be obtained at any drug store. 



