Comparative Electro-Physiology: A Physico-Physiological Study

Photographic Record of Conversion of the Abnormal Di-phasic hitn . Normal Negative, after Tetanisation,.T, in. Nerve of Fern Photographic Record showing how the Abnormal Positive Response is converted through’ Diphasic into Normal Negative by the ' Increasing Effective Intensity of Stimulus, due to Lessening the . Distance between the Responding and Stimulated Points. . Diagrammatic Representation of the Conductivity Balance . : Photographic Record made during Preliminary Adjustment fay Balance of Nerve of Fern . ‘ ‘ é : ‘ ;

Effect of Na,CO, Solution on Responsive Excitability a F Bee s Nerve Photographic -Record showing iighsocemeat o Rimehivile by Application of CaCl, . . - Photographic Record showing Haviedslcn of Rendaastie Excitability by Application of KCl . Photographic Record exhibiting Comparative Effects of NaCl tad NaBr on Responsivity Photographic Record of Effect Fi Dilute (* 5 per cee. ) Sates of Giistageanis Record of Effect of Stronger Dobe: (2 per ents i) of

RESPONSIVITY versus CONDUCTIVITY under Nal . Effect of Alcohol on the Responsivity of Frog’s Nerve Photographic Record of Effect of Alcohol Vapour on Receptivity: - Photographic Record of Effect of Alcohof on Conductivity . . . Photographic Record showing Effect. of Alcohol on Responsivity - Diagrammatic Representation of Experimental Arrangement’ for ’ Demonstration. of RECEPTIVITY versus CONDUCTIVITY, or of RECEPTIVITY versus RESPONSIVITY . ne haere RECEPTIVITY versus RESPONSIVITY under Alcohol Photographic Record aan Effect of spsiii on » Cohductivity of PjJant-nerve. : . . .

The Cork Chamber for Gradual Raising of the Temperature of one Arm of the Balance .- : Photographic Record Skiing Effect of Riau Tenipedsaded on Conductivity i Experimental Arrangement for Riadyiing ‘After- effect of Seances on Conductivity and Excitability : Photographic Record Showing Effect of ‘ Mosiaeate Siteaniatiend in Enhancing Conductivity and Excitability - Photographic Record showing Effect of Excessive Stimulation i in De- pressing Excitability and Conductivity Record of Contractile Response in Frog’s Nerve indi Contiawdus Electric Tetanisation .

Diagrammatic Representation of meee for Obtaining Petes. mitted Effect of Stimulus . Photographic Record of Effect of aia on pivecbanines Resneiize -of Frog’s Nerve . : . Photographic Record showing Abobasis of Mechanics Response oa Frog’s Nerve by Action of Solution of Morphia Photographic Record showing Preliminary Exaltation in Mechsnical Response of Frog’s Nerve after Application of Alcohol ‘ Photographic Record showing Effect of Chloroform on Mechanical Response of Frog’s Nerve .

. . Photographic Record showing Mocornal hace commento’ into Photographic Records showing Gradual Dldatpéatanice oe Positive ‘Element in diphasic Mechanical Responses of Frog’s Nerve and Plant-nerve . . Photographic Record sional Sinairense Effect in Medalees Re- . . Photographic Reproduction of Recon of Méckanicat Rea ponus af Frog’s Nerve and Plant-nerve obtained on Smoked Glass Surface of Oscillating Recorder 324. Record of Mechanical Responses to Electrical Stamatis chaaiviell on. Smoked Glass, and given by the Optic Nerve of Fish Ophiocephalus 325. Record, obtained on Smoked Glass, of Transmitted Effect of Stimu- lation on Nerve of Gecko . , z ee 326. . Initiation of Multiple Response by Drying of Ne erve : . ‘327. . Diagrammatic Representation of Experimental Arrangement for Re- : cording Response by Resistivity Variation . 328. . Photographic Record of the Morographic Curve takin by Method of ; Resistivity Variation in Pistil of Hibiscus. Critical point of in- version at 60°8° C, . ‘ 329. Photographic Record of the Morographic aes ken os Method of Eléctromotive Variation in’ Petiole of JZusa. Critical point of inversion at 59:6° C. . 330. Photographic Record of the Morgeaphie Cave ‘sane by Method of

Mechanical Response in Filament of Passifora. Critical point of Response Records by Resistivity Variation, in the Nerve of Fern Effect of Chloroform seen in benim i of ee tg dk in Frog’s Nerve . Photographic Record of Effect of ali dienes in Enhancing Mechani- cal Response of Plant-nerve . Photographic Record showing Bekeucemeat of Excitability dndér Action of Light in Nerve of Fern Distribution of Fibro-vascular Elements in Siigle Sane of Stem df Papaya

Extra-polar Electrotonic Effects under an Maiae E. M. F, shins rises from *6 to 1°4 Volts . : Diagram illustrating Bernstein’s Dechanieat of Kat- cbiitioale Caiént Diagram illustrating Bernstein’s Decrement of An-electrotonic Current Diagram representing Hermann’s Polarisation-increment under Tetanising Shocks, with reversed polarising Current Diagram representing Hermann’s Polarisation-increment fades Tetanising Shocks, with reversed polarising Current :

Experiment with Petiole of Fern demonstrating Variation of Cou ductivity by Polarising Current, Excitation travelling electrically Downhill : Experiment with Petiole of Fern desisghstraliais Masten of Bex: ductivity by Polarising Current, Excitation travelling electrically Uphill é ‘ Photographic Records of Rassonaes salons in last inegariseents when Excitation was transmitted with and against the Polarising Current. Photographic Record of Modification of Conduction during Passage of Excitation from Anodic to Kathodic Region, under Increasing Intensity of Polarising E.M.F.

Photographic Record showing Eshanced Condectizin fie Kathodic to Anodic Region . Experimental Arrangement to Exhibit the eliccnmnent of xciat bility at Anode, when the Acting E.M.F. is feeble Experimental Arrangement to Exhibit Depression of Excitability a at Kathode, when the Acting E.M.F. is feeble . Photographic Records of Response, illustrating the Hevanchebiews: bf Excitability at Anode, and Depression at Kathode, under Feeble Acting E.M.F. in two Specimens of Nerve of Fern a and é. :

Experimental Arrangement demonstrating the Joint Effects of Variation of Conductivity and Excitability by Polarising Current . Experimental Arrangement demonstrating the Joint Effects of Variation of Conductivity and Excitability by Polarising Current, when Current is Reversed . ‘ Photographic Record of Response under the Kerapasenenis given in Figs. 351, 352 in Nerve of Fern Experimental Arrangements for Showing so- called Polatisn tan: increment by the Joint Effect of Increased Excitability at Anode and Enhanced Conduction of Excitation electrically Uphill .

Experimental Arrangements for Showing so-called Polarisation- increment by the Joint Effect of Increased Excitability at Anode and Enhanced Conduction of Excitation electrically Uphill. Direction of Current in this is Reversed : Photographic Record of Responses in Nerve of Fern, andes Anite and Kathodic Action as described in Figs. 354 and 355. Effect of Anode and Kathode on Responsive Sensation in er Hand Polar Effects of Cureate ia to Eoclned Aprile on ones Half of Pulvinus of Erythrina indica 7

Experimental Arrangement for Magnetometric. Method of Recard Photographic Record of Periodic Groupings in Magnetic Responses Photographic Record of Response and Recovery of Steel under Moderate and strong Magnetic Stimulus Photographic Record showing Ineffective Stimulus made Effective by Repetition Photographic Record of Response of prin esiaaine Powder in Sugpish Condition to Stimulus of Electric Radiation Photographic Record Showing Uniform Response of -Ahenvbetocn Powder to Uniform Stimulus of Electric Radiation .

Experimental Arrangement for obtaining Response in iro * i duction Current : ; Process of Balancing illustrated by Pivotopra pate Record af Reiponnes. Gradual Enhancement of Conductivity by the Action of Stiendies Characteristic Curve of Iron under increasing Force of Magnetisation . Characteristic Conductivity Curve of Sensitive Metallic Particles be- longing to Negative Class, under increasing Electro-motive Force. Photographic Record of Magnetic Tetanisation of Steel, éthiblting Transient Enhancement of aba Speed on Cessation .

Mechanical Response of Frog’s Nerve to successive equal Stimuli, applied at Intervals of One Minute Mechanical Response of Frog’s Nerve, showing Conversion of Ab- normal Positive into Normal Negative Response after Tetanisation . Photographic Record showing Conversion of Abnormal ‘ Down’ Re- Gradual Transformation from <Abonrek: to Normal Response in Platinum ; Normal Electro-motive Resnse 3 in Tin, sakuiced after Tetkiteation Photographic Record of Abnormal Response of Selenium Cel con-

Photographic Record showing Moderate Normal Geshcees of Sclendigs enhanced after Tetanisation Photographic Record of Abnormal aN e unpeied to Electric -Radiation, converted after Tetanisation into Diphasic and Normal . Moderate Normal Response of Aluminium, enhanced after Tetanis- ation Photographic Record of Eahansemeat of ‘Mieneue neseouse aier Tetanisation Vertical Series of Recsds sowie Tensiorantion of iioecisl rao Normal Response after Tetanisation in Living and Inorganic alike in the A phase

Series showing how Delamighon etieecese: ee Ressnien' in ‘the B Phase . Photographic Racorit storing Responses niaadian with different Photographic Record of Response of Tungsten zh as finkance- ment of Response after moderate Tetanisation, and Reversal of Response, due to Fatigue under stronger Tetanisation . . Series showing reversal of Normal Response by mee due to cong Fatigue in Indiarubber giving rise to Dinkaue ana: Beveyied Re- sponses Fatigue age ss Diphasic Variation ana Reversal of N Scania Response in Frog’s Nerve

Abnormal Response of ae ty Rieiasiobisens followed ii et Response of Contraction Record of Response in Nerve of Gecke showing the Effect of eat metically increasing Stimulus : : Response of Nerve of Bull-frog to Stimuli 1, 2, a peo Bs is Rn in Arithmetical Progression . Response of Optic Nerve of Ophioephalus e Arithmetically i sicenaiite Stimuli 1, 2, 3, 4, 5,6, 7 . ‘ Mechanical Response of Nerve of Fern to Arithmetiealy i increasing Stimulus Photographic Record my Magretic “Responses in Steel t to Arith- metically increasing Stimulus . : ‘ . - :

Response to stimulus by change of form—Permeability variation—Variation of solubility — Method of resistivity variation: (a) positive variation ; (4) negative variation—Sign of response changed under different molecular modifications—Response of vegetable tissue by variation of electrical re- sistance—Response by~electro-motive variation in inorganic substances— The method of block—Positive and negative responses—Similar responses in living tissues—Effects of fatigue, stimulants, and poisons on inorganic and

organic responses — Method of relative depression, or negative variation, so called, IN studying the properties of living tissues, we find one of their most important characteristics is found in the fact that they exhibit the state of excitation under the impact of stimulus. On the cessation of stimulus, again, the excited tissue returns to its original condition. The excitatory change thus undergone is fundamentally due to the derangement, or upset, of the molecules of the living tissue from their normal equilibrium, recovery being brought about by their restoration to that state. The excitatory condition is sometimes shown by change of form, as in the case of the shortened length of excited muscle (fig. 1). This might be compared with the shortening of stretched india-rubber under ther- *'~ ees ei rirstheag mal stimulus (fig. 2).

Now it is clear that the molecular change consequent on excitation must occasion various concomitant physical changes, and it should be theoretically possible to detect and measure this induced molecular change by recording such concomitant variations, Thus the stimulus of light, for example, may induce a mole- cular change which may in its turn induce, say, a variation in the permeability of the sub- stance to liquid. Bichromated gelatine becomes less perme- able under the action of light. The solubility of a substance Fic. 2. Response of India-rubber may again undergo variation sepsis ini ty nO at under external stimulus —sul- phur, for example, usually soluble in carbon disulphide, is rendered insoluble under the action of light.

In order, then, to study the effect of a given stimulus with accuracy, we should be able to detect and measure the extent of the changes induced. The two effects which have just been referred to are not, as will be seen, highly susceptible of accurate measurement. But in the detection of molecular changes by electrical means, we have at our disposal methods -for the measurement of such changes, the ease and delicacy of which leave nothing to be desired. Two such methods may be used—that of Resistivity and that of Electro-motive Variation. According to the method of resistivity variation, the substance to be experimented on is placed in an electrical circuit, including a delicate galvanometer and a suitable electro-motive force, such as to cause a small deflection of the galvanometer. The impact of the stimulus on the sub- stance under examination now induces in it a molecular change by which its resistance is made to undergo a variation, which in the case of certain substances may be an increase, or in that of others adiminution. On the cessation of external stimulus, the substance shows recovery, with a corresponding return to its original conductivity. Thus in the case of selenium, for instance, the conductivity is increased, or the

resistance decreased, under the action of light. In fig. 3 is shown a number of responses to light, given on a series of separate exposures, each of one second’s duration, the inter- vening periods allowed for recovery being of one minute each. Fic. 3. Response of Selenium to the Stimulus of Light (Resistivity variation method) These responses were obtained by recording the increased deflection due to decreased resistance under the impact of light, and the subsequent recovery. Such responses, by means of decreased resistance, we may arbitrarily distinguish as negative. Similar responses are also given by a mass of metallic particles when acted upon by electric radiation. In fig. 4 are seen several of these negative responses given by galena under the action of this stimulus. There are, on the _ other hand, some substances: which _ give positive responses ; that is to aes ee SPORE oF Soul say, their resistance is increased, (Resistivity variation method) or conductivity decreased, under the action of stimulus. The deflection of the galvanometer under a constant electro-motive force now undergoes diminu- tion during the impact of stimulus. Such positive responses

of response does not depend on the electro-positivity or negativity of the substance is seen in the fact that while highly electro-positive potassium gives positive response, the equally electro-negative dioxide of lead gives a response of the same sign. Substances like magnesium, aluminium, and iron give negative response. It is found, again, that the same substance, under different molecular conditions, will give responses of opposite signs. For example, a particular molecular variety of silver, Ag’, gives positive (fig. 5), whereas ordinary silver gives nega- tive response. Again, while Ag’ normally gives positive, yet the sign of this response is gradually reversed to nega- tive, under the long-continued action of very strong stimulus. By the employment of the same method of resistivity variation, I have been able to obtain excitatory response records from living tissues also. Details of these will be given in a subsequent chapter.

The electric response, however, employed to obtain the excitatory reaction of living tissues, depends upon the electro-motive variation of the substance under stimulation. This electric reaction has. been regarded as vitalistic in contradistinction to physical. But I have shown that similar responses are given by inorganic substances also. That is to say, the molecular excitability on which the phenomenon of response depends is not distinctive of animal tissues alone, but is common to all matter, both organic and inorganic. If, then, we desire to understand those funda- mental reactions which underlie the response of living tissues, it will be well to observe its occurrence in the much simpler case of the inorganic body.'

' For a detailed account cf, Bose, Aesponse in the Living and the Non- Living. wire, and if its molecular condition be the same throughout, it is obvious that its physical properties will likewise be uniform. Hence its electrical condition will also be the same at every point; in other words, it will be iso-electric. But if a portion of this wire should now be made to undergo a molecular change, as, say, by hammering, the physical condition of this portion will be made different from that of the rest. There will, therefore, be an electrical difference, and the wire will no longer be iso-electric. This fact can be verified by making suitable connections between the molecularly strained and unstrained portions of the wire, and a galvanometer, when a current will be found to flow through the galvanometer, showing that a difference of electrical potential has been brought about by the induced

(a) Method of block; (4) Equal and opposite responses when the ends A and B are stimulated ; the dotted portions of the curves show recovery ; (c) Balancing effect, R, when both the ends are stimulated simultaneously. inequality of molecular conditions in different parts of the same wire. I shall now describe the method by which electrical responses to molecular disturbance may be obtained from inorganic substances. For this purpose, two different methods may be employed—first, the method of block, and, secondly, the method of relative depression. According to the first of these, the wire to be experimented on is held clamped at the middle, electrical connections being made with a galvanometer at two points, A and B, by means of two non-polarisable electrodes (fig. 6). We may now produce

excitation of the A end of the wire, by imparting a torsional vibration, the molecular disturbance being prevented from reaching the B end by the intervening block. Using this method of experiment, I have obtained with different sub- stances two different types of response—namely, positive and negative. In the positive, the responsive current flows through the wire from the unexcited to the excited, or towards the excited—that is to say, the excited point becomes galvanometrically positive. Responses of this kind are given by tin, zinc, platinum, and other metals. In fig. 7 is seen a uniform series of such responses to uniform stimulus. The intensity of the response, moreover, does not appear to depend on the chemical activity of the substance. For the response of the chemi- cally inactive tin is much stronger than that of the active zinc. The very inactive platinum is also found to give a fairly strong response, although the electrolytic contacts are made with pure water.

The electro-motive response may also be obtained by other modes of molecular excitation. Thus, instead of torsional, we may use longitudinal vibration. A metallic rod of brass, AC, is clamped in the middle. A thin copper wire is led sideways from the clamp and connected with a piece of brass, B. A and B are connected with a galvanometer by means of non-polarisable electrodes. If now the C end of the rod be rubbed with resined cloth, A may be thrown into longitudinal vibration, B being little affected by this. It is here interesting to observe the concomitance of the electrical response with the sonorous tesponse of the rod, and the dying of the electrical response with the waning of the musical note. The stronger the molecular vibration, the stronger the sound, and also the stronger the response. The direction of the responsive current in the metal is from the less excited B to the more excited A.

that when a substance is molecularly modified, the sign of its response tends to be reversed. Thus, as already said, ordinary silver gives positive, and modified silver, Ag’, negative response. But the latter, under strong and long- continued stimulation, has its response re-converted, as it were, to the normal positive. In the same way, under the method of electro-motive variation also, we find the normal positive response of, say, tin, or platinum, becoming con- verted by molecular modification into negative, to be again re- converted under continuous stimulation to the normal positive.