STIMULATION BY THE MINERAL ACIDS, HYDROCHLORIC, SULFURIC, AND NITRIC, IN THE SUNFISH EUPOMOTIS

1. The stimulating efficiency of hydrochloric, sulfuric, and nitric acids has been measured in the sunfish Eupomotis gibbosus, by a method which reduces experimental errors to a minimum. 2. The results show that stimulation by these acids is primarily dependent upon the (H(+)) produced in the animal's aquatic environment, and that the reaction time is a logarithmic function of the (H(+)) within the range tested expressed by the equation: (RT–5) = –4.3 log (H(+) x 10(4)) + 9.118. 3. Any effect of the chloride, sulfate, and nitrate ions must itself be measured by the (H(+)). 4. Variation in the reaction time is also a logarithmic function of the (H(+)), and the percentage variation is independent of the (H(+)) over the range tested. 5. Freshly collected fish show a lower threshold for stimulation as determined by the (H(+)) than do fish adapted to laboratory conditions, but relatively the reaction times of the two groups are the same.