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The animal emerges on land; and, with a better supply of oxygen and less loss of heat, all the functions are performed with the highest possible efficiency. First, apparently, amphibia, then reptiles, and finally mammals of enormous size and strength appeared. It looked as if the earth were to be an arena where gigantic beasts fought a never-ending battle of brute force. But these great brutes reproduced slowly, had therefore little power of adaptation, were fitted to special conditions, and when the conditions changed they disappeared. The bird tried once more the experiment of developing the locomotive powers to the highest possible extent. It became a flying machine, and every organ was moulded to suit this life. Every ounce of spare weight was thrown aside, the muscles were wonderfully arranged and of the highest possible efficiency. The body temperature is higher than that of mammals. The whole organization is a physiological high-pressure engine. The sense-organs are perhaps the finest and keenest in the whole animal kingdom. The brain is inferior only to that of mammals. The experiment could not have been tried under more favorable conditions; it was not a failure, it certainly was not a success when compared with that of mam
been practically exhausted. Only brain development The possibilities of every system except one had remained as the last hope of success. Here was an untried line, and the mammals followed it. short tertiary period the brain in many of their genera
seems to have increased tenfold.
By the arboreal life
of the highest forms the hand is developed as the in
strument of the thinking brain.
The battle is begin
ning to become one of wits, and the crown will soon pass from the strongest to the shrewdest. Mind, not muscle, much less digestion or reproduction, is the goal of the animal kingdom. And we shall see later that the mammalian mode of reproduction and of care of the young led to an almost purely mental and moral advance. For these could have but one logical outcome, family life. And the family is the foundation of society. And family and social life have been the school in which man has been compelled to learn the moral lessons, the application of which has made him what he is.
You must all, I think, have noticed that the different systems of organs succeed one another in a certain definite order; and that each stage from the lowest to the highest is characterized by the predominance of a certain function or group of functions. This sequence of functions is not a deduction but a fact. Place side by side all possible 'genealogical trees of the animal
kingdom, whether founded on
comparative anatomy, embryology, paleontology, or all combined. I will all disclose this sequence of functions arranged in the same order. Let me call your attention to the fact that this order is not due to chance, but rests upon a physiological basis. We might almost claim that if the evolution of man from the single cell be granted, no other order of their occurrence is possible.
The protozoa are mostly, though not purely, nutri
I reproductive. These functions are essential to the existence of the species. Naturally in the early protozoan colonies, and in forms like hydra, these funcenough for digestion. Muscles are needed to draw the
tions predominated. But mere
food to the mouth, to keep the digestive sack in contact with it, and for other purposes. A little higher they are used to enable the animal to go in search of its food. They are still, however, more or less entirely subservient to digestion. But in the highest worms we are beginning to see signs that muscles are predominating in the body; and we feel that, while mutually helpful, the digestive system exists for the muscles, and these latter are becoming the aim of development. From worms upward there is a marked advance in physical activity and strength. The muscles thicken and are arranged in heavier bands. Skeleton and locomotive appendages and jaws follow in insects and vertebrates. The direct battle of animal against animal, and of strength opposed to strength or activity, becomes ever sharper. The strongest and most active
are selected and survive.
And yet this is not the whole truth. of perception is possessed by every animal. muscles had developed the nervous system could be of but little practical value. Knowledge of even a great emergency is of little use, if I can do nothing about it. But when the muscles appeared, nerves and ganglion cells were necessary to stimulate and control them. And this highest system holds for a long time a position subordinate to that of the lower muscular organ. seems at first sight extraordinarily slow. Only in insects and vertebrates has it become a centre of instinct and thought. Through the senseknowledge of its environment. it is gaining an ever clearer, deeper, and wider
First it is affected
only by the lower stimuli of touch, taste, and smell.
cognizance of ever subtler forces and movements. Memory comes into activity very early. The animal begins to learn by experience. The brain is becoming not merely a steering but a thinking organ. More and more nervous material is crowded into it and detailed for its work. Wits and shrewdness are beginning to count for something in the battle. Not only the animal with the strongest muscles, but the one with the best brain survives. And thus at last the brain began to develop with a rapidity as remarkable as its long delay. Thus each higher function is called into activity by the next lower, serves this at first, and only later attains its supremacy.
And yet the advance of the different functions is not altogether successive. Muscle and nerve do not wait for digestion and reproduction to show signs of halting before they begin to advance. They all advance at once. But the progress of reproduction and digestion is most rapid at first, and it appears as if they would outrun the others. But in the ascending series the others follow after, and soon overtake and pass by them. And these lower functions, when outmarched, do not lag behind, but keep in touch with the others, forming the rear-guard and supply-train of the army. And notice that each organ holds the predominance about as long as it shows the power of rapid improvement. The length of its reign is pretty
digestive system reaches that limit early, the muscular system is capable of indefinitely higher complexity, as we see in our hand. But the muscular system has yor quite reached its limit. The body had seen its day of dominance before man arrived on the globe.
But where is the limit to man's mental or moral powers? Every upward step in knowledge, wisdom, and righteousness only opens our eyes to greater heights, before unperceived and still to be attained. These capacities, even to our dim vision, are evidently capable of an indefinite, perhaps infinite, development. What, as yet only partially developed, faculty remains to supersede them? As being capable of an endless development and without a rival, may we not, must we not, consider them as ends in themselves? They are evidently what we are here for. Everything points to a spiritual end in animal evolution. The line of development is from the predominantly material to the predominance of the non-material. Not that the material is to be crowded out. It is to reach its highest The body development in the service of the mind. must be sustained and perfected, but it is not the end. The goal is mind, the body is of subordinate impor
But if this is true, we must study carefully the development of mind in the animal.
presses upon us; if there is a sequence of physical functions in animal development, is there not perhaps also a sequence in the development of the mental faculties? What is the crowning faculty of the human mind and how is its fuller development to be attained? Let us pass therefore to the question of mind
in the animal kingdom.