4 
Expt. 2.—I chilled the skin with rhigolene in the same place without freez¬ 
ing, again producing laboured breathing. Within half a minute the bird began 
to move backwards. As I now felt sure that the spinal centres could not have 
been reached by the cold, I secured them from all possible chance of this in the 
following way:— 
Expt. 3.—A fresh pigeon was held by an assistant, Dr. Wilson, while I 
picked up and held between my thumb and finger a portion of the loose cer¬ 
vical skin. The part which projected above my hold was thus removed at 
least three-quarters of an inch from the spine, while I lightly froze it with the 
rhigolene jet. Before releasing the bird, I carefully held the skin until it re¬ 
gained its natural warmth, when I set the pigeon at liberty. To my surprise, 
it showed, in two or three minutes, the utmost confusion of movement, with 
finally very perfect backward motions. f 
In another experiment, like the last in all other respects, I warmed the 
frozen skin before I let the bird go, but the result was nevertheless iden¬ 
tical. I now perceived that the phenomena which could be caused by 
directly chilling the spine, were to be obtained in a less striking manner, 
but still very remarkably, by merely chilling or freezing the skin of the 
back of the neck, and that I had before me one of the most beautiful illus¬ 
trations of reflex pathological movements which had as yet been dis¬ 
covered. 
The next experiments it is needless to relate in full. They were directed 
towards ascertaining the amount of cold which it was requisite to produce 
in order to occasion the retrograde actions. I found that while for their 
best display it was well to freeze the skin, in many cases it was only 
necessary to chill the surface very lightly to get the effect in a form quite 
sufficiently clear. The extent to which it is desirable to chill or freeze 
seemed to be determined solely by the individuality of the pigeon itself, 
since in some a single flash, so to speak, of the rhigolene would answer, 
while in others I obtained the retrogressive actions only by intensely 
freezing the skin, or even, in rare cases, not at all. It was also well 
worthy of note that in pigeons which did not at first yield the usual 
movements, several repetitions would occasion them, and that afterwards 
they became easy of production. Moreover, as a rule, each successive 
exhibition appeared to make the pigeon more readily liable to the motions 
referred to, so that in some cases, which at first required firm freezing to 
cause the spasms, even the slightest chilling would suffice. 
When fully satisfied that the curious enforced movements above described 
were due merely to reflex effects, and not to any direct chilling of the spine, 
I proceeded with care to determine the relation between the region of skin 
frozen or cooled and the form of the resultant phenomena. 
Head .—When the skin of the head over the cerebrum is seized between 
the fingers, and frozen and thawed before releasing it, there are sometimes 
seen, at the start, irregular and confused movements. These, as a rule, 
result in stupor so deep that the bird, if carefully handled, may be laid on 
its back and left without stirring for many minutes. In general, it starts 
