W. H. R. Rivers and Henry Head

“ Fewer difficulties surround the testing of sensibility to cold; but it must be remembered that a silver tube always seems colder than one of glass containing water at the same temperature, on account of the greater rapidity with which it abstracts heat. Cold stimuli, more particularly those used for testing cold-spots, are liable to cause a vaso-constriction, shown by a blanching of the skin. This condition is peculiarly unfavourable for all sensory tests. ”

“ Any profound cooling of the skin, or even the occurrence of a pilomotor reflex, greatly diminishes the accuracy of the answers to compass stimulation. When the coat is removed, and the sleeve is rolled up, "goose-skin" is frequently produced; testing should not be begun until this has entirely passed away.
We always began a series of tests with the compass-points widely separated from one another (9 cm.) . Not uncommonly the records considerably improved as the distance was gradually diminished, and were frequently better at 7 cm. than at 9 cm. ”

“ Gentle stroking with cotton wool is not a specific stimulus to hair-clad parts, as far as the peripheral nervous system is concerned. Since the whole of the area affected by our experiment was covered with long hairs, we have always used this test, both before and after shaving. It is no easy task to shave the forearm and back of the hand so cleanly that no stumps project above the surface of the skin. ”

“ On a later occasion, observations were made by stimulating the normal right hand covered with a thin rubber glove, when H. noted that the quality of the touches resembled that experienced from the abnormal area.
The most extended observations were made on the back of the affected hand, because of the rapidity with which sensation began to return to the skin of the forearm. But during the short time at our disposal, the anæsthetic parts of the forearm were found to behave exactly in the same way as the insensitive area on the dorsum of the hand. ”

“ H. soon learnt to differentiate this pain, due to a hot object, from a true sensation of heat; he frequently said, "Any ordinary patient would have called such stimuli hot, because the pain produced is of a kind associated in daily life with the action of hot bodies only. Further, a patient is told to say if he feels heat, cold, or a touch. Given, then, that he knows his thermal sensibility is being tested, he would certainly call the sensation I experience 'hot.'"
Occasionally, contact with a neutral tube would cause an indeterminate and somewhat tingling sensation over the affected area ”

“ He was able to reproduce the image of a thing seen with such accuracy that it could be searched for details, at first unnoticed. But this was not the case with any other sensory impression. As soon as the stimulus was removed, he retained so much only as had been noticed at the time; for he was unable to reproduce any sensory images, except those of vision. This peculiarity common to most of those who visualize strongly leads to the following difficulty in testing sensation. Suppose that H. was returning correct answers to stimuli of different kinds applied to the affected area ”

“ A low external temperature greatly increased the difficulty in discovering both heat- and cold-spots; and in the winter, when the affected hand seemed numb and cold, previous immersion in warm water greatly facilitated their determination.
To test the power of discriminating two points we used a pair of carpenter's compasses, the points of which had been ground down until they gave no sensation of sharpness. [3] For recording our observations, we used the method suggested by McDougall [22] . The compass-points were set at a certain distance from one another ”

“ They were never warmed or cooled from without. When used for testing sensibility to heat, several tubes ranged in a wooden stand were filled with water at temperatures considerably higher than those we wished to use for testing; from these, a tube was selected as soon as it had sunk to the temperature required. These silver tubes lose their heat so rapidly that it is possible to use the same one for a short series of tests only. ”

“ Every thought is in some way bound up with internal vision, and even numbers, the days of the week and abstract ideas, such as virtue and cowardice, are associated with images of varying tones of white and black. ”

“ The more gradually contact was established between the stimulating object and the affected part, and the smaller the pressure applied, the less likely was it that a sensation would result. All our observations showed that parts endowed with deep sensibility only are especially sensitive to jarring impact.
Not even stimulation with No. 8 of von Frey's hairs could be recognized, when applied to the affected area on the back of the hand. ”

“ This sleepy condition which is so favourable for results with compasses is one that requires absolute freedom from all external appeal to responsible action. It is a condition which H. has never succeeded in producing surrounded by the multifarious interruptions of home.
Conversely, concentration on the details of the compass-test greatly diminished the accuracy of H.'s answers. ”

“ This was a somewhat tiresome procedure and materially disturbed the sensibility of the affected area. Such marking should never be undertaken shortly before sensory tests are employed. Moreover, it is extremely difficult, even with the greatest care, to ensure the exact correspondence of the squares on different occasions. The skin on the back of the hand is extraordinarily flexible, and any change in the position of the fingers modifies the size and appearance of the squares to a remarkable degree. ”

“ So large a block of copper retains its heat for a considerable time, and the thermometer gives a sufficient indication of its temperature. This should lie between 50° C. and 40° C, preferably at about 45° C. Higher temperatures cause distinct pain, which complicates the observations; a temperature below 40° C. fails to stimulate most of the heat-spots. ”

“ This discovery did not receive the attention which was due to it, because it seemed to be little more than the last stone necessary to support the universally accepted hypothesis of "muscular sense."
But we long ago suspected that the existence of so many afferent fibres in the muscular nerves was not connected with the power of estimating movement only. ”

“ The smooth surface was passed across the skin, and then the cylinders were made to project until a sense of roughness or "raking" was produced. In every case, the most careful comparative observations were made over similar parts of the sound limb. ”

“ But von Frey states ( [11] pp. 223 to 229) that this is not a correct method of comparing hairs which are used as graduated tactile stimuli. For this purpose he divides the pressure in milligrammes by the radius of a circle of the same area as the elliptical section of the hair. The result expressed in grm./mm. will be found in the last column of the following table:—
Towards the end of our research, we received a second set of hairs from Professor von Frey which were useful in measuring the punctate pressure capable of producing cutaneous pain. ”

“ The results were remarkable, and it could not be said that there was any difference between the two hands in the quickness and accuracy with which pressure, touches were localized.
R. chose nine spots in various parts of the affected area unknown to H.; these are marked in black on the annexed figures (figs. 15 and 16) . The following table gives the places stimulated in order and the position of the spots marked by H. on his photograph:—
(2) Localized exactly.
(3) Localized 1·3 cm. from the spot touched. ”

“ Head, Rivers and Sherren. "The Afferent Nervous System from a New Aspect," Brain, 1905, vol. xxviii., p. 99. Idem and Sherren. "The Consequences of Injury to the Peripheral Nerves in Man," Brain, 1905, vol. ”

“ Idem. "Ueber d. sog. perversen Temperaturempfindungen," Skand, Archiv f. Physiol., 1906, Bd. xviii., S. 166. Blix, Magnus. "Experimentelle Beiträge zur Lösung der Frage über die specifische Energie der Hautnerven" (1 and 2) , Zeitschr. f. ”