Page:Mind (New Series) Volume 6.djvu/463

 NOTES AND NEWS. 447 rather difficult to recognise. From the cold -spots I have been able to get sensations of cold not only during the current but also when making or breaking it. From the warm-spots only during it, and even then with difficulty. The skin gets brown, a thick yellow fluid coming forth. The spots cannot react afterwards, at least for some time, as thej" are destroyed ; whether they can be regenerated, I am not at present prepared to say. INADEQUATE THERMAL STIMULATION. (1) v. Frey 7 describes a phenomenon which he has called "paradox sensation of cold ," and which consists in the fact that cold-spots (some of them) can be made to give sensations of cold when stimulated with warm metal-points of 45 C. and upwards. When trying to test this observation, I thought first that the sensations were due merely to mechanical stimulation. I soon found, however, that this could not be the case, for when I increased the temperature of the points more and more (at last up to + 100 C.), the sensations of cold were also found to become stronger and stronger. The crucial test I made by using a small convex lens, through which sunrays were allowed to pass and which I held at such a distance from the skin that the focus fell on a cold-spot. By screwing the lens in a certain manner (so as to get just the proper amount of warmth on the cold-spot) I could distinctly observe sensations of cold, when the spots were excited in this way. By mapping out cold- spots with cold points and afterwards letting another person stimulate my skin with hot points (+75- 100 C.), while I kept my eyes shut, I obtained also in this case an objective proof of the truth of v. Frey's dis- covery the possible workings of my imagination being thus eliminated. This observation is, according to my opinion, of the greatest importance for the understanding of the sensation of " heat ". I hope to be allowed to treat of this in a following paper. (2) Naturally I have tried to find out if "paradox sensations of warmth " also exist. But the stimulation of warm-spots with metal-points of all degrees of cold (down to about - 70 C.) did not bring forth any sensa- tions of warmth. CHEMICAL STIMULATION. As chemical substances are known to stimulate the skin, I wanted to try their effect when strongly localised to sense-spots. By applying small drops of different substances in liquid form (nitric and sulphuric acid (cone.) and alkali), the cold-spots were found to give sensations of cold, the warm-spots of warmth. No sensations of warmth or cold could be had from other spots of the skin. SENSATIONS OF PRESSURE. As far as I have been able to observe, the temperature-spots are not in the same degree capable of sensations of pressure (tactile-sensations) as the so-called "pressure-spots" (Blix, Goldacheider, v. Frey); i.e., the former need just as the skin in general stronger pressure than the latter before sensation ensues. SENSATIONS OF PAIN. When wishing to ascertain if the temperature-spots are sensible to pain, care must be taken to get a sensation of cold (warmth) from the spot marked as a cold- (warm) spot, because without such a sensation there is no surety that the spot itself has been attained by the stimulus applied ; exciting then the spots with various kinds of stimulus capable