In certain cases Goldscheider succeeded in getting sensation of temperature by electrical stimulation of the nerve-trunks in the arm, back of the hand, &c. These observations I have also repeated, using very strong electrical currents which gave almost continuous pain, as recommended by Goldscheider. By stimulating nerves in the back of the hand, I have succeeded in getting peripheral sensations of both heat and cold, the latter sensation being the more frequent. The sensation was localised in small areas in all the cases which I observed. I am able also to corroborate his statement that the discriminative sensibility is much finer for temperature than for tactile sensations. Since the receipt of Goldscheider's paper, I have been able to make one independent contribution to this subject, which, so far as I am aware, is new. Dr. M. Warfield called my attention, a short time since, to the fact that in a certain operation on the eye by Dr. Russell Murdoch, cocaine having been used, the patient recognised the presence of the knife on the eye by a sensation of cold. By the courtesy of Dr. Murdoch, I was enabled to examine the eyes of several patients at the Baltimore Eye and Ear Hospital. When the eye in these cases was completely insensible to pain, and felt no contact whatever, cold and warm bodies were readily distinguished. This observation I have been able to repeat on my own eye. By means of 5 per cent. solution of muriate of cocaine the eye was rendered completely insensitive to pain or contact, but still readily felt heat and cold. Here we have the 1 At the end of a brief account of this action of cocaine, published in the Maryland Medical Journal, I requested observations on the temperature-sense by those who had occasion to use cocaine in the throat. Dr. John N. Mackenzie at once took up the matter, and has kindly furnished me the following summary of his results : "Six patients were taken for experiment. The uvula and soft palate, and afterwards the nasal passages, were first bathed in a 4 per cent. solution of the muriate of cocaine. When anasthesia of the parts was complete, a silver probe, which had been previously immersed in a mixture of ice and salt, was carried over the parts, rendered beforehand insensible to contact and pain, as tested in various ways. A distinct sensation of cold was in every instance complained of. "The opposite extremities of the same probe were next heated over the argand burner of a lamp used for laryngoscopic purposes, and in its heated condition made to impinge upon various spots in the anæsthetised area. While absolutely no pain was felt by any of those experimented upon, there was a marked unanimity of the answers in regard to the sensation of heat. In three of the cases, the application of the heated probe left an eschar, and in one a pretty severe pharyngitis developed, yet at the time of application no pain was felt, though the temperature-sense remained intact. None of the patients were aware of the purpose of the experiments. or the previous preparation of the probe." temperature-sensations completely isolated from the other dermal sensations in a way which is now capable of easy repetition, and important as furnishing another argument for the independence of the thermal apparatus. 3. Theoretical. The wider bearings of these results have been insisted on by both Blix and Goldscheider, but it may not be amiss to call attention to them here. The view of Weber (5), that we have but a single apparatus for both pressure and temperature, was mainly based on the fact that he did not succeed it separating the spots on the skin from which the two sensations were roused, and that a cold body felt heavier, a warm one lighter, than one at the temperature of the skin. But Szabadföldi (8), using disks of wood heated to 50° C. and above, found that warm bodies were felt heavier than those not warmed, so that the force of the latter argument is much weakened. Wunderli's (9) experiments showed that at obtuse points, as on the back, a touch with cotton wool and the approach of a warm body were sometimes confounded. If these experiments are taken to show a common origin for temperature and sensation of pressure, which by no means they do, then, as Blix points out, we must admit that heat, cold, and pressure of a certain grade are all identical, an idea which is absurd. Against the view of Weber, there was, from the start, the objection that the temperature-sensations and discriminative sensibility did not vary pari passu, as might have been expected from his theory. Further, there is the pathological evidence. Brown-Séquard (10), and also other observers, have noticed that, in certain cases where the sensibility of the skin is abnormal, the pressure-sense and temperature-sense are not equally affected; in fact, in some cases one may entirely disappear and the other remain intact. Evidence has also been brought forward to show that these two sensations pursue different paths in the cord. Recently Adamkiewicz (11) has called attention to the fact that a sinapism has a different effect on temperature and tactile sensibility, for the sinapism causes no effects of transfer for temperature, while it does for the tactile sensations. Herzen (12) has found that when the arm is made to fall "asleep" tactile sensibility is first abolished, then sensibility to pain; with the former the sensibility to cold disappears, while that for heat remains and does not disappear until the arm becomes insensitive to pain. Testing the rapidity of the transmission for the sensations of heat and cold, he found that the relative rapidity was as 3 to 2. He adds the clinical fact of a woman who had no sensation of temperature from bodies below 27° C. In this case the post-mortem showed the posterior columns of the cord in an atrophied condition. He suggests then that the sensations of cold and pressure pass through the posterior columns, while heat and painful sensations are transmitted by the grey matter. As bearing directly on this question, the action of cocaine above described may be referred to. Brücke (13) has called attention to the fact that in some cases we get different reflexes according as pressure or thermal stimulus is used. The recent writers, Funke (14), Hering (15), and others, have assumed a special apparatus for the temperature-sensations on account of the distinct modality of the two sensations. So far as I know, the observations of Herzen (12), mentioned above, are the most important evidence for the duality of the temperaturesense itself. Previously, there were various theories current as to how one apparatus could give rise to two sensations as clearly distinct as those of heat and cold. Weber (5) put forward the view that it was the act of rising or falling in temperature which roused the thermal sensations. Vierordt (16) explained it as due to the direction in which heat was passing when the current was directed from without inwards, we had the sensation of warmth; when from within outwards, the sensation of cold. Hering, relying mainly on his contrast- and exhaustion-experiments, considers that we have a single apparatus excitable in two ways, the two sensibilities standing in such relations to one another that, as one is exhausted, the other is reinforced. Goldscheider (12) rejects this notion of the double action of a thermal stimulus, on the ground of certain experiments mentioned in the first part of this paper. I have repeated these experiments and can fully confirm the results. We have then to look upon our temperature-sensations as mediated by two distinct sets of nerves, each set being quite independent of the other. The excitement of one set gives a characteristic sensation recognised as cold; the other, a different sensation recognised as heat. The theory cannot be made to turn on the question as to whether the special nerve is gaining or losing heat; for, as these experiments show, the results can all be obtained with mechanical stimulation. As regards the after-action, on which so much stress has been laid, this, as Goldscheider remarks, is a purely nervous phenomenon quite independent of any changes of temperature. The bearing of these observations on the measurement of the sensibility to temperature-differences is considerable, and there seems little doubt that the work designed to test the application of the psychophysical law to the skin-with its great averageerror-will have to be at least reviewed in the light of these new observations. As to their influence on the methods of testing 416 H. H. DONALDSON: ON THE TEMPERATURE-SENSE. the skin, it would be unsafe to predict. Eulenberg (3), in a very recent paper, advances the idea that both for pressure and temperature we must still, as in the past, test on surfaces and not on points. This investigation has brought to light some new facts and results, which have, without doubt, their greatest importance in controlling other lines of work. Some of these results, as I have endeavoured to show, were independently worked out in this Laboratory: but, in presenting a claim for independence, I hope that I have still made it clear that to Blix belongs the priority; that Goldscheider's paper is very careful and complete ; and that I am in a large measure indebted to both these ob servers. My thanks are due to Prof. G. Stanley Hall for his aid and advice during this work. I also gladly take this opportunity to thank all those who have kindly placed themselves and their time at my disposal for experiment, and otherwise assisted me in this research. References to Literature. (1) Magnus Blix: Zeitscher f. Biol., Bd. xx., Heft 2; 1884. (2) A. Goldscheider: Monatshefte f. prakt. Dermatol., Bd. iii., Nos. 7, 9, 10; 1884. (3) Eulenberg: Nature, Vol. xxxi., No. 7944; Jan. 15, 1885. Monatshefte f. prakt. Dermatol., Bd. iv., No. 1; 1885. (4) A. Goldscheider: Monatshefte f. prakt. Dermatol., Bd. iv., No. 1; 1885. (5) E. H. Weber: Wagner's Handwörterbuch d. Physiol. Archiv. f. physio log. Heilkunde; 1856. (6) Lussana: Archiv. Ital. d. Biolog. Fasc. iii. ; 1883. (10) Brown-Séquard: Jour. de Physiol., Vol. viii.; 1863. Archives de Physiol., Vol. i.; 1868. (11) Adamkiewicz: Berlin-Klin. Wochenschr., Nos. 12, 13; 1881. (12) Herzen: Revue Méd. d. l. Suisse rom. Vol. iii., p. 372; 1883. (13) Brücke: Vorlesungen ü. Physiol. ; 1881. (14) Funke: Hermann's Handb. der Physiol., Bd. iii., Th. 2, s. 289. (15) Hering: Hermann's Handb., Bd. iii., Th. 2, s. 415. (16) Vierordt: Grundriss d. Physiol., 5te Aufl., s. 355; 1877. 23rd March, 1885. VI. DISCUSSION. MILL'S PROPOSITIONS AND INFERENCES OF MERE EXISTENCE. BY J. H. LEVY. IN considering Mill's doctrine on this subject, it is best to commence with his statements respecting inductions of bare existence. These alleged results of the inductive process may be considered the summa genera of such forms of predication; and it will be convenient to start from them and work downwards. "With respect to general propositions of this class," says Mill, "that is, which affirm the bare fact of existence, they have a peculiarity which renders the logical treatment of them a very easy matter; they are generalisations which are sufficiently proved by a single instance. That ghosts, or unicorns, or seaserpents exist, would be fully established if it could be ascertained positively that such things had been even once seen. Whatever has once happened is capable of happening again; the only question relates to the conditions under which it happens. So far, therefore, as relates to simple existence, the Inductive Logic has no knots to untie." Now, I quite agree that "as relates to simple existence, the Inductive Logic has no knots to untie". But, where there are no knots naturally, we may, through that maladroitness in holding the threads of a complex investigation which is more or less an attribute of every human being, make a tangle; and that, in my opinion, has been done. It will always be to me a puzzle how a man of Mill's ability could so easily have reconciled himself to the notion that there is a whole class of generalisations each of which is (or may be) proved by a single instance. If this were true, instead of dismissing it with the remark that it affords Inductive Logic no knots to untie, I would say that it would be so extraordinary a phenomenon that, until it was adequately accounted for, the foundations of inference would remain a mystery. I would first contend" with respect to general propositions of " existence, that they do not exist, or-to put the matter more clearly-that these alleged general propositions are not general at all. A general proposition is one actually or potentially in the form "Every x is y". In propositions of existence, y = existent; 'System of Logic, vol. ii., pp. 143-4. |