REPORT UPON A PARASITIC PROTOZOAN. 



187 



8. Large aquaria, 4 feet deep ; about 25 pounds of 



salt placed in each aquarium. Fresh lake 

 water was constantly running in at the sur- 

 face, but no attempt was made to force air 

 through the water. Experiment performed 

 by the attendants of the aquarium. 



9. Methylen blue, 1 per cent aq. sol., 1 cc. ; lake 



water, 200 cc. 



10. Methylen blue, 1 per centaq. sol., 10 cc; lake 



water. 200 cc. 



11. Methylen blue, 1 per cent aq. sol.,20cc.; lake 



water, 2,000 cc. 



12. Methylen blue, 1 per cent aq. sol., 15 cc. ; lake 



water, 500 cc. 



Tanks contained badly infested trout and catfish. 

 Most of them stood tbe test well, and after 

 two weeks the infection was greatly lessened. 

 Some of the fish, however, still bad parasites. 



(a) Trout alive at end of 2 minutes. Parasite also 

 alive. 



(b) Trout died in 18 minutes. 



Trout alive; parasites unaffected at end of 5 min- 

 utes. 



Trout unaffected at end of an hour. Parasites 

 on fish still alive; those which escaped from 

 the fish die in the solution. 



Parasites, upon being freed from the fish and 

 placed in this solution, died in 12 minutes. 

 Trout were unaffected at the end of an hour. 



For experiments Nos. to 12 no air-pressure was available; temperature varied 

 from 22° O. to 24° C. 



13. Lake water, 10 L. ; methylen blue, 1 per cent Friday, 5 p.m. Five small trout badly infested, 

 aq. sol., 30 cc. ; constant aeration. 22° to three of the fish very weak. 



24° C. Saturday, 9 a, m. One trout dead. 



Sunday, 9 a. m. One trout dead. 



Monday, 9 a. m. One trout dead. 



Wednesday, 9 a. m. Two catfish added. 



Many of the parasites had fallen from the fish, and considerable scum had left 

 them. This scum, together with the parasites, was colored blue by the methylen blue, 

 and the solution was much weakened; 30 cc. 1 per cent methylen blue was added. 



Friday, 9 a. m. One catfish dead ; the trout had 

 lost most of their parasites. 



Monday, 12 m. Trout entirely free from para- 

 sites; a few parasites left on the catfish. 



From this experiment it is evident that methylen blue is a substance which may 

 be used to kill the parasites. It is, however, fatal to the fish if used in too strong- 

 solution, or if the fish are very weak. Although this experiment does not justify the 

 unqualified use of methylen blue, it is very suggestive as pointing out a line for future 

 research and experiment. 



14. Eosin, 1 per cent aq. sol., 5 cc. ; lake water, 



500 cc. 



15. Eosin, 1 per cent aq. sol., 15 cc. ; lake water, 



500 cc. 



16. Lake water, 10 L. Eosin 1 per cent aq. sol., 



60 cc. 23° C, constant aeration. 



17. Eosin solutions used in experiments 14 to 16 



kill the free protozoa in 15 to 60 minutes. 



Poth fish (trout) and parasites alive after 10 



minutes. 

 Trout unaffected after two hours ; parasites on fish 



still alive ; those which fell from the fish died. 

 Friday, 5 p. m., 2 trout. 

 Monday, 9 a. m., 2 catfish. 

 Wednesday, 9 a. m., all alive. 

 The parasites have lessened in number; accident 



to jar ends experiment. 



As the fish live very well in these solutions, eosin can be looked upon as another 

 possible remedy for parasitical diseases of fish. 



At the same time that the above 17 experiments were made, numerous other experi- 

 ments were also carried on. Although the details of some of the other experiments will 

 be given below, as of possible use to anyone who takes up this subject in the future, 

 I am inclined to look upon the experiments thus far given as the most suggestive for 

 future work. It was my intention to experiment with these three substances — salt, 

 methylen blue, and eosin — on a much larger scale, but at this point a combination of 

 circumstances prevented my carrying out the matter further. 



