Response in the Living and Non-Living | Page 3

POISON IN ABOLISHING RESPONSE IN NERVE 139
89. ACTION OF STIMULANT ON TIN 141
90. ACTION OF STIMULANT ON PLATINUM 142
91. DEPRESSING EFFECT OF KBr ON TIN 143
92. ABOLITION OF RESPONSE IN METALS BY 'POISON' 143
93. 'MOLECULAR ARREST' BY THE ACTION OF 'POISON' 145
94. OPPOSITE EFFECTS OF SMALL AND LARGE DOSES ON THE 146 RESPONSE IN METALS
95. RETINAL RESPONSE TO LIGHT 150
96. RESPONSE OF SENSITIVE CELL TO LIGHT 152
97. TYPICAL EXPERIMENT ON THE E.M. VARIATION PRODUCED BY 154 LIGHT
98. MODIFICATION OF THE PHOTO-SENSITIVE CELL 155
99. RESPONSES IN FROG'S RETINA 156
100. RESPONSES IN SENSITIVE PHOTO-CELL 157
101. EFFECT OF TEMPERATURE ON THE RESPONSE TO LIGHT 159 STIMULUS
102. EFFECT OF DURATION OF EXPOSURE ON THE RESPONSE 159
103. RESPONSES OF SENSITIVE CELL TO INCREASING 161 INTENSITIES OF LIGHT
104. RELATION BETWEEN THE INTENSITY OF LIGHT AND 162 MAGNITUDE OF RESPONSE
105. AFTER-OSCILLATION 163
106. TRANSIENT POSITIVE INCREASE OF RESPONSE IN THE 164 FROG'S RETINA ON THE CESSATION OF LIGHT
107. TRANSIENT POSITIVE INCREASE OF RESPONSE IN THE 165 SENSITIVE CELL
108. DECLINE UNDER THE CONTINUOUS ACTION OF LIGHT 166
109. CERTAIN AFTER-EFFECTS OF LIGHT 168
110. AFTER-EFFECT OF LIGHT OF SHORT DURATION 172
111. STEREOSCOPIC DESIGN FOR THE EXHIBITION OF BINOCULAR 176 ALTERNATION OF VISION
112. UNIFORM RESPONSES IN NERVE, PLANT, AND METAL 184
113. FATIGUE IN MUSCLE, PLANT, AND METAL 185
114. 'STAIRCASE' EFFECT IN MUSCLE, PLANT, AND METAL 186
115. INCREASE OF RESPONSE AFTER CONTINUOUS STIMULATION IN 186 NERVE AND METAL
116. MODIFIED ABNORMAL RESPONSE IN NERVE AND METAL 187 TRANSFORMED INTO NORMAL RESPONSE AFTER CONTINUOUS STIMULATION
117. ACTION OF THE SAME 'POISON' IN THE ABOLITION OF 189 RESPONSE IN NERVE, PLANT, AND METAL

RESPONSE
IN THE
LIVING AND NON-LIVING
CHAPTER I
THE MECHANICAL RESPONSE OF LIVING SUBSTANCES
Mechanical response--Different kinds of stimuli--Myograph--Characteristics of response-curve: period, amplitude, form--Modification of response-curves.
One of the most striking effects of external disturbance on certain types of living substance is a visible change of form. Thus, a piece of muscle when pinched contracts. The external disturbance which produced this change is called the stimulus. The body which is thus capable of responding is said to be irritable or excitable. A stimulus thus produces a state of excitability which may sometimes be expressed by change of form.
#Mechanical response to different kinds of stimuli.#--This reaction under stimulus is seen even in the lowest organisms; in some of the amoeboid rhizopods, for instance. These lumpy protoplasmic bodies, usually elongated while creeping, if mechanically jarred, contract into a spherical form. If, instead of mechanical disturbance, we apply salt solution, they again contract, in the same way as before. Similar effects are produced by sudden illumination, or by rise of temperature, or by electric shock. A living substance may thus be put into an excitatory state by either mechanical, chemical, thermal, electrical, or light stimulus. Not only does the point stimulated show the effect of stimulus, but that effect may sometimes be conducted even to a considerable distance. This power of conducting stimulus, though common to all living substances, is present in very different degrees. While in some forms of animal tissue irritation spreads, at a very slow rate, only to points in close neighbourhood, in other forms, as for example in nerves, conduction is very rapid and reaches far.
The visible mode of response by change of form may perhaps be best studied in a piece of muscle. When this is pinched, or an electrical shock is sent through it, it becomes shorter and broader. A responsive twitch is thus produced. The excitatory state then disappears, and the muscle is seen to relax into its normal form.
#Mechanical lever recorder.#--In the case of contraction of muscle, the effect is very quick, the twitch takes place in too short a time for detailed observation by ordinary means. A myographic apparatus is therefore used, by means of which the changes in the muscle are self-recorded. Thus we obtain a history of its change and recovery from the change. The muscle is connected to one end of a writing lever. When the muscle contracts, the tracing point is pulled up in one direction, say to the right. The extent of this pull depends on the amount of contraction. A band of paper or a revolving drum-surface moves at a uniform speed at right angles to the direction of motion of the writing lever. When the muscle recovers from the stimulus, it relaxes into its original form, and the writing point traces the recovery as it moves now to the left, regaining its first position. A curve is thus described, the rising portion of which is due to contraction, and the falling portion to relaxation or recovery. The ordinate of the curve represents the intensity of response, and the abscissa the time (fig.?1).
[Illustration: FIG.?1.--MECHANICAL LEVER RECORDER The muscle M with the attached bone is securely held at one end, the other end being connected with the writing lever. Under the action of stimulus the contracting muscle pulls the lever