196 PROCEEDINGS OF THE AMERICAN ACADEMY. 



been performed. This method of procedure separated the cord from 

 the brain, but did not interfere with the vital centres in the latter nor 

 with the sympathetic system. These frogs were tested several times, 

 for the two or three days during which they lived, by suspending 

 them at the anterior end in such a way that the hind legs could be 

 subjected to various stimuli. All of these individuals flexed the legs 

 when they were touched with a brush which had been moistened 

 in ten per cent acetic acid, and four of them reacted in the same 

 manner when the light and heat from a Nernst lamp was thrown on 

 the skin, a lens being used to bring the light to a focus ; but not a 

 single individual reacted to light from this lamp when the heat rays 

 were cut off by interposing a fiat-sided jar filled with water. 



Ten toads were tested by the same methods as those used for the 

 frogs, and, though they reacted to acid and the light with heat, no 

 reactions were obtained when light alone was used. 



As no photic reactions had been obtained from spinal frogs or toads, 

 it was thought that such responses might be induced if the animals 

 were rendered more sensitive ; and experiments were accordingly 

 undertaken in which the diencephalon and cord were transected in 

 nine toads and 0.001 grain of strychnine inserted into the dorsal lymph 

 space through a small slit in the skin. The individuals which had been 

 treated in this manner were extremely sensitive to tactual stimuli, and 

 the slightest jar of the table on which they were supported sufficed to 

 throw their limbs into a state of spasmodic extension. When, however, 

 a beam of light was focussed on the hind leg of such an individual, no 

 indubitable responses were obtained. 



Since the attempts to induce photic reactions in terrestrial am- 

 phibians had met with no success after the brain had been separated 

 from the cord, I next turned my attention to the available aquatic 

 species. The eyes were removed from a single Cryptobranchus, and 

 its cord was cut behind the first vertebra. This individual was then 

 placed in an aquarium, and light from a Nernst lamp was focussed 

 upon its skin in various regions ; and, although it had been found 

 to be extremely responsive to light after the eyes had been removed, 

 no such responses were obtained from it after the cord had been cut. 

 It nevertheless continued to respond to tactual stimulation, and when 

 the side was stroked gently with the finger, it jerked its legs and drew 

 its tail away from the stimulated region. Chemical stimulation was 

 also effective after the cord had been cut, for when a pellet of cotton 

 moistened with ten per cent acetic acid was placed so that it touched 

 the tail, the body was bent away from the stimulated area. 



As the experiments with Cryptobranchus had given only negative 



