Page:Popular Science Monthly Volume 14.djvu/386

372 a solution of curari is injected under the skin than when the dry poison is introduced by the point of an arrow. Vigorous animals with rapid circulation of blood are more easily poisoned than those which are weakly; and with an equal dose of poison and with animals of equal size, those whose temperature is constant die more quickly than those whose temperature is variable (reptiles, batrachians, fishes), and, among the former, birds succumb more quickly than mammals.

The animal at first does not feel the wound, for curari possesses no caustic property. In the case of very small animals death is almost instantaneous. In birds and mammals of a large size, and in all animals of variable temperature, death usually occurs in from five to twelve minutes, if there is an excess of the poison. The animal lies down as though it would sleep, keeping the eyes open, with a placid expression. Soon it is seized with a progressive paralysis of the motor nerves, proceeding from the extremities to the centre. The muscles of respiratory movement are the last to succumb, and the animal dies from asphyxia.

To all appearance, nothing could be calmer than this progressive state of stupor; there is no agitation, no expression of suffering. The mouth remains shut, without foam or saliva. Life seems to be extinguished slowly, like some liquid that gradually flows away. In view of these treacherous symptoms, a member of the Society for the Prevention of Cruelty to Animals might be tempted to urge the use of curari in lieu of the brutal modes at present in vogue for slaughtering old, worn-out horses.

To Claude Bernard science is indebted for the exact determination of the specific action of curari. Vital activity presents a threefold series of distinct and coördinated organic elements, which play the part of excitants of one another. The starting-point of physiological action is the sensitive nerve-element. Its vibration is transmitted along its axis, and on reaching the nerve-cell—a regular relay—the sensory vibration is transformed into a motor vibration. This latter, in turn, is propagated through the motor nerve-element, and on reaching its peripheric extremity causes the fibre of the muscle to vibrate, and this, reacting in virtue of its essential property, produces contraction, and consequently motion.

Now, each of the three elements, sensory, motor, and muscular, lives and dies after a fashion of its own, and there are poisons proper to each. But, inasmuch as vital manifestations require the coöperation of these three activities, if one be suppressed, the other two continue to live indeed, but they no longer mean anything, just as a phrase loses its meaning if one of its members be dropped out. Claude Bernard's experiments have proved that the motor nerve-element alone is affected by curari, and that the other two organic elements of the animal retain their physiological properties. The mind is not destroyed, the muscular fibre still has the power of contraction, and indeed does contract under the influence of electric discharges. Motor power alone is