CHAPTER IV
THE GENERAL EFFECT OF STIMULATION
Contents: Various examples of the effects of stimulation. Metabolism of rest and metabolism of stimulation. Metabolic equilibrium. Disturbances of equilibrium by stimuli. Quantitative and qualitative alterations of the metabolism of rest under the influence of stimuli. Excitation and depression. Specific energy of living substance. Qualitative alterations of the specific metabolism and their relations to pathology. Functional and cytoplastic stimuli. Relations of the cytoplastic effects of stimuli to the functional. Hypertrophy of activity and atrophy of inactivity. Metabolic alterations during growth of the cell. Primary and secondary effects of stimulation. Scheme of effects of stimulation.
In the foregoing lectures we have had occasion to touch more or less often on the subject of the effects of the stimuli. This was the case, however, only when it appeared necessary to obtain a systematic knowledge of the stimuli and the differentiation of the individual factors. We will now proceed to consider the effect of stimulation in a more systematic manner. The conditional method of observation, however, will remain our guide.
We have already pointed out the relations between the conception of stimulation and that of vital conditions, now we will consider that of the effect of stimulation with that of vital processes. Nevertheless, the effect of stimulation being a manifestation of the vital process is not, therefore, in opposition to the latter as such. Hence the question presents itself as to the connections between vital process and the effect of stimulation.
When we study the motile flagellate infusorium Peranema swimming undisturbed in water, we observe that the swimming movements are absolutely regular in character. The elongated cell body remains unaltered in shape. The long flagellum is extended in a perfectly straight line in the axis of the body and only the extreme end lashes with regularity through the water (Figure [8], A). There is majestic grace in this perfect uniformity of motion. The picture suddenly alters the moment the Peranema is influenced by the slightest jar. The whole flagellum at once executes a few violent movements (Figure [8], B), the body draws together, soon stretches itself again and swims immediately after, in another direction, with the same majestic calm as before.
Fig. 8.
Peranema. A—Swimming in non-stimulated condition. B—Mechanically stimulated at the end of the flagellum.
Another instance. A number of fertilized eggs of the sea urchin are placed in a watch glass in sea water. The temperature of the water should correspond with the mean temperature in which the animals live in the sea, averaging about 15° C. The eggs begin to form grooves and to develop slowly by progressive division. In another glass we observe a second sample of fertilized eggs of the same kind and under the same conditions, but in this case we increase the temperature to 25° C. The increased temperature brings about a decided increase of segmentation and the same stage of development is reached in less than half the time. The increased temperature, therefore, increases the development. Further we take a third sample of the same urchin eggs in a watch glass with sea water of 15° C. and add a little sea water mixed with ether. The development of the eggs now comes to a standstill. The narcotic has produced an inhibition of development.
To quote another instance. Bacterium phosphorescens having been bred upon a putrid fish are exposed in the culture fluid to the air. In the dark the bacteria give forth a phosphorescent light. Then the culture fluid containing the bacteria is put into a glass receptacle, which can be rendered air-tight and all oxygen excluded. After a short time the light formation ceases completely. The absence of oxygen has here had a depressing effect and it is only after air has been again introduced that light is once more produced.