FiTCHETT. — Physiological Action of Tutin. 



307 



responds to a dose of 10 to 40 mlgm. per kilo. For example, if we consider 

 that a dose of tiitin — say, 10 mlgm. per kilo — injected under the skin of a 

 mammal becomes rapidly and equally diffused through all parts of the 

 body, its concentration at any point would be 001 gram (10 mlgm.) per 

 thousand. In the case of a fish floating in a solution of tutin, the amount 

 of the fluid is so much larger than the fish that the diffusion of the tutin 

 into its body will not materially reduce the concentration of the poison in 

 the fluid, and so the tissues of the fish will be subjected to the action of 

 0-001 per cent., or 10 mlgm. per kilo. The fatal dose in fish may there- 

 fore be said to be about 40 mlgm. per kilo under these experimental condi- 

 tions. 



Table III. 

 Fishes (Trout-fry). — Minimum Lethal Dose. 



It was intended to use trout-fry in experiments that were made to com- 

 pare the action of tutin with that of other members of the same group, 

 and to test the effect of remedies ; but the supply suddenly failed, so re- 

 course was had to another small fish, known locally as the minnow, which 

 aboiinds at certain seasons of the year in the waters of the Otago Harbour 

 and Lake Logan. This fish [Galaxias attenuatus) is peculiar to the South 

 Island of New Zealand, Tasmania, and Tierra del Fuego (33). It mea- 

 sures 1-3J in. long, is equally at home in brackish and fresh water, and will 

 live in a trough in the laboratory for weeks if fed on Liver and supplied 

 with fresh running water. It is semi-transparent, and the heart can be 

 seen beating. After a great many experiments it was found that the best 

 results were obtained when three fish were used, and placed in a fairly wide 

 (7-in.-diameter) enamelled bowl, containing 1,000 c.c. fluid. It was found 

 necessary to almost completely cover the top of the bowl with a piece of 

 wood, for if left uncovered the fish were apt to leap out. This happened 

 several times, andjwas often more aggravating to the experimenter than 



