Of all mammals guinea-pigs are most susceptible to fright. Simply taking hold of them, and keeping them a moment in the hand without any pressure, is often sufficient to paralyse them with fear. Guinea-pigs may remain half an hour in this state, rabbits not more than ten minutes, while frogs will remain for hours without moving. It is impossible that this interval be spent in sleep, for the animals expel fæces and urine. Kirchner maintained the necessity of drawing a white line from the beak of the animal, so that it should imagine itself bound by this mark; but this is not true, as they remain just as motionless without the line, and cataplexy is even more easily produced when the animal sees nothing. Crabs taken out of the water allow themselves to be put into the strangest positions, and remain for a long time motionless. Preyer made similar experiments on frogs and mice.[32] Some serpents remain rigid when their head is slightly pressed, as Moses is said to have done before Pharaoh. [31] From [Greek: kataplêx], [Greek: êgos], frightened. [32] W. Preyer: _Die Kataplexie_. Jena, 1878. To produce this state a sudden, unexpected agitation is necessary; it is a matter of indifference in what way the animal is treated, as all depends on the violent fright caused. A similar condition has been observed in men struck by lightning and in animals after electrical discharges from a powerful machine. Many birds, though scarcely wounded by small shot, fall to the ground as though struck by lightning, panting, with wide-open eyes, and remaining motionless when placed on their back. This also is an instance of the cataplectic condition, for, as their wound is not mortal, nor even serious, they recover soon afterwards. Some animals and many insects remain for a long time motionless when danger threatens. To one of these zoologists have given the name of _anobium_, as though it feigned death when touched. Many other coleoptera act in the same way, not even moving when they are caught, transfixed with a pin, and roasted over a flame. Preyer justly remarks that this cannot be a feint, nor an instinct which tells them to preserve the appearance of death as a means of saving their life; for it would then be incomprehensible that they should let themselves be burnt alive rather than abandon the deception. Certainly an animal that does not move can more easily escape from an enemy. Darwin remarks that when an animal is alarmed, it stops an instant to collect its senses and discover the source of the danger, and decide whether it should escape or defend itself; but this is certainly not the origin and reason of the phenomena of cataplexy and fear, which we must consider as a serious imperfection in the animal organism.