PHYSICAL ANTECEDENTS OF SCIENCE 123

through the spinal cord to the brain, and so produce feeling,

because the brain is the main organ of sensation. The

influence outwards appears to travel downwards from the

brain, which is, ordinarily, the main fundamental agent for

producing motion, and onwards down the spinal cord, and

thence to the muscles, which thus move in response to

a surface stimulus which has been felt. But when the

spinal cord has been divided it becomes no longer possible

for such influences to ascend to the brain (and, therefore,

there can be no feeling), or to descend from the brain (and,

therefore, there can be no voluntary motion). But the

unfelt influence travelling inwards is supposed, in that case,

on reaching the spinal cord, to be thence automatically

reflected outwards. That such is the case appears to be

shown by the fact that appropriate movements are made

in response, but made without the intervention of the will.

Reflex action may also take place when the body is quite un-

injured, as during sleep, under the influence of chloroform, etc.

But this kind of action is much more strikingly dis-

played in some of the lower animals. A frog which has

had its head cut off will yet make with its hind legs

appropriate movements to remove any irritating object

applied to the hinder part of its body. If its skin be

touched with some caustic fluid, one leg will be brought

forward so that the foot may be applied to the irritated

spot; and if that leg be held, then the other leg will

be similarly moved forwards. A more striking instance

of the same power can be obtained from the same kind

of animal at the breeding season. The male frog has the

habit of tightly grasping the female, and to enable him the

more securely to maintain his hold, a warty prominence

becomes developed on the inner side of each of his fore-feet.

Now, if such a male frog be taken, and not only decapitated,

but the whole hinder part of the body also removed, so that

through the spinal cord to the brain, and so produce feeling,

because the brain is the main organ of sensation. The

influence outwards appears to travel downwards from the

brain, which is, ordinarily, the main fundamental agent for

producing motion, and onwards down the spinal cord, and

thence to the muscles, which thus move in response to

a surface stimulus which has been felt. But when the

spinal cord has been divided it becomes no longer possible

for such influences to ascend to the brain (and, therefore,

there can be no feeling), or to descend from the brain (and,

therefore, there can be no voluntary motion). But the

unfelt influence travelling inwards is supposed, in that case,

on reaching the spinal cord, to be thence automatically

reflected outwards. That such is the case appears to be

shown by the fact that appropriate movements are made

in response, but made without the intervention of the will.

Reflex action may also take place when the body is quite un-

injured, as during sleep, under the influence of chloroform, etc.

But this kind of action is much more strikingly dis-

played in some of the lower animals. A frog which has

had its head cut off will yet make with its hind legs

appropriate movements to remove any irritating object

applied to the hinder part of its body. If its skin be

touched with some caustic fluid, one leg will be brought

forward so that the foot may be applied to the irritated

spot; and if that leg be held, then the other leg will

be similarly moved forwards. A more striking instance

of the same power can be obtained from the same kind

of animal at the breeding season. The male frog has the

habit of tightly grasping the female, and to enable him the

more securely to maintain his hold, a warty prominence

becomes developed on the inner side of each of his fore-feet.

Now, if such a male frog be taken, and not only decapitated,

but the whole hinder part of the body also removed, so that