by a more gradual process. As a matter of fact it is found that in this, as in other provinces of nature, the law holds good.

When we increase the rate at which the development of an organism proceeds, the results of the development are less stable, are more easily varied and disordered than when development proceeds more slowly. Thus we find that domesticated animals, in which the capacity to mature early has been implanted by cross-breeding, and carefully nursed by selection, are far more prone to vary, are less uniform in character, resemble one another far less closely than wild. animals of the same species whose development is more gradual; and we find, moreover, that domesticated animals are more subject to disease than wild ones. The tendency

of precocious children to die young has become a matter of notoriety. But the most frequent and most conspicuous result of an undue rapidity of development, and especially of the last stages of development, is unstability of the highest nervous arrangements. We have seen that a certain degree of instability is essential to the constitution of the nervous system, and without this instability it cannot act. Hence it will naturally happen that when the organism as a whole is less stably constituted than usual, the increase of instability will be especially marked in that tissue which is normally less stable than the rest. If the nervous system, and especially its highest regions, be more than usually unstable, what will be the result? Broadly speaking, the results will be as follows.

The normal instability being increased, the normal discharges will take place on less provocation than in more stably constituted individuals. Reaction will take place on slighter impressions. Hence we find that cross-bred animals, which are distinguished on the one hand by early maturity, that is to say by rapid development, are distinguished also by their wildness. "Thus the Earl of Powis formerly imported some thoroughly domesticated humped cattle from India, and crossed them with English breeds, which belong

to a distinct species; and his agent remarked to me, without any question having been asked, how oddly wild the crossbred animals were." "Sir F. Darwin crossed a sow of the latter [Chinese domesticated] breed with a wild Alpine boar which had become extremely tame, but the young, though having half-domesticated blood in their veins, were extremely wild in confinement." "Captain Hutton, in India, crossed a tame goat with a wild one from the Himalayas, and he remarked to me how surprisingly wild the offspring were." The same peculiarity has been noticed in pheasants, fowls, ducks, finches, and other animals. Now the character which distinguishes wild animals from tame ones is their much more energetic reaction to slight impressions. The snapping of a twig, a distant footstep, a whiff of scent from an animal passing far away, is enough to make the wild animal start up on the alert, to put every muscle in his body in a state of tension in readiness for instant flight, or to scare him into headlong activity. The tame animal, on the other hand, will bear to be approached, spoken to, patted, scratched, and punched without being roused out of his sluggish contentment.

Not only will the more rapidly developed, and therefore more unstable, organism react to slighter impressions than the slower growing and more stable individual, but to impressions of the same intensity the former will react more vigorously. Hence they will be generally of greater activity, capable of stronger, more rapid, and more sustained movement than the stably constituted organism. The wildness of crossed species, which is from one point of view a reaction to slighter impressions, is from another point of view a more vigorous reaction to impressions of equal intensity. The crossing of varieties and races and "strains " produces invariably, with the increase of size and the earlier maturity, on which we have already insisted, an increase of vigour in

· Darwin, “Variation of Animals and Plants under Domestication," 1875, vol. ii. p. 19.

the offspring; that is to say, an increase in the energy of their reaction to impressions.

From our present point of view, the most important result of an undue rapidity of the process of development is the structural instability of the tissues so developed. When the highest nerve regions attain completion very early in life as the result of an unduly rapid development, they will be unduly liable to derangement upon slight provocation; and hence we find that very precocious children are very liable to nervous disorders; and that such individuals, on attaining adult age, are very liable to insanity. "There be some,' says Bacon, "have an over early ripeness in their years, which fadeth betimes."

There is yet another aspect of this subject that has to be considered. Height of intelligence depends in the main upon height of development; but one element in high intelligence is the readiness with which the higher regions of the nerve tissue undergo rearrangement. The more easily new combinations of cells and fibres are formed, the more readily new channels can be excavated in the grey matter, the greater the facility with which rearrangements and recombinations are effected, the more easily can new courses of conduct and new modes of thought be originated, and the more complex are the reactions that the individual can effect upon his circumstances. Now this readiness to undergo rearrangement is, of course, in other terms, mobility or instability of the nerve tissue, and, as such, is greatly favoured by rapidity of development. Rapidity of development, as it is a factor in the production of insanity, is also therefore a factor in the production of high intelligence, and thus there is a sound scientific basis for the saying of Dryden that

"Great wits to madness sure are near allied,
And thin partitions do their bounds divide.”

Hence we shall expect to find that those individuals who develop rapidly will as a rule be more intelligent than those who develop slowly, and this we find to be the case; for, as

a rule, it is undoubted that the intelligent child makes the clever man and the backward child the dull man. The rule is of course not without exceptions, for, as we have already seen, height of intelligence depends essentially on extent of development, and the more rapid process of development does not necessarily proceed further than the slower one. Hence we sometimes come across an individual who was dull in childhood and youth, and developed later in life a high degree of intelligence. In such individuals the intelligence will be of very stable and enduring character.

On every hand we have evidence of the truth of our main proposition, that the more rapid the development of the highest nervous centres, the less stable is the result. We have now to notice that this instability may reach so high a degree as to surpass the limits of the normal. The reaction to impressions may be so vigorous as to be manifestly in excess: conduct may become outrageous. Or, to put it more accurately, a certain amount of decomposition of the nerve tissue we have seen to be necessary for the performance of the function of that tissue. This decomposition is in normal organisms prevented, by the inherent stability of their tissue, from occurring in excess. But, when the tissues are unduly unstable, and the check on its progress is diminished, it may easily take place in such excess as to produce actual disorganization of the highest nervous regions; which disorganization is, as we have seen, the physical defect which underlies insanity. Doubtless it sometimes, though rarely, happens that an organism developes with great rapidity and yet presents no evidence or no striking evidence of instability; but this may be accounted for by its possession of what, for want of a better term, I must call momentum. We have already seen how the heavy ball, from its greater momentum presses steadily forwards when the light one, proceeding at even a higher velocity, is diverted from its course; and similarly a railway train that is to travel at a very high speed is made very heavy. If it is too light it will be apt to run off the line.

There seems to be some analogous property in developing organisms which enables those which possess it in a high degree to proceed straight onward in spite of a high velocity, while those in which it is wanting are easily diverted from their course.

The conclusions at which we arrive with regard to the bearing of the second law of inheritance upon the production of insanity are therefore these :—

1. When the germ starts upon its course of development with an insufficient impetus, the development of the organism in general, and the highest nervous regions in particular, will be incomplete; and this incompleteness, when slight, will show itself as feebleness of mind, when considerable as imbecility, and when extreme as idiocy. A still greater defect in the impetus will result in the nonproduction of living offspring.

2. When the impetus given to the germ is such that development proceeds with undue speed, the later stages will be apt to be faulty, and the organism so developed will be unstable, and will be prone to insanity.