"In a similar manner, a particle of contagium spreads through the human body and may be so multiplied as to strike down whole populations. Consider the effect produced upon the system by a microscopic quantity of the virus of small-pox. That virus is, to all intents and purposes, a seed. It is sown as yeast is sown; it grows and multiplies as yeast grows and multiplies, and it always reproduces itself."

Such germs may be scattered by the breath, or through perspiration, or be carried in the garments. It matters little, however, how they are carried (as to their practical effects), for they are no respecters of persons, provided they find parties or substances which are susceptible to their influences. These germs being seeds, the person attacked by them receives them as a field does the seeds of grain or vegetables. It matters not whether these seeds are large enough to be seen by the eye, or so fine that they cannot be seen even with a microscope; they are still seeds, and their progeny often increase and multiply as rapidly as do thistles when sown in a rich soil. I cannot better close the consideration on this point than by quoting from Prof. Tyndall's "Floating Matter of the Air,” pp. 254, 255:

"Thus far, I think, we have made our footing sure. Let us proceed. Chop up a beefsteak and allow it to remain. for two or three hours just covered with warm water; you thus extract the juice of the beef in a concentrated form. By properly boiling the liquid and filtering it you can obtain from it a perfectly transparent beef-tea. Expose a number of vessels containing this tea to the moteless air of your chamber; and expose a number of vessels containing precisely the same liquid to the dust-laden air. In three days every one of the latter stinks, and, examined with the micro

scope every one of them is found swarming with the bacteria of putrefaction. After three months, or three years, the beef-tea within the chamber, if properly sterilized in the first instance, will be found as sweet and clear, and as free from bacteria, as it was at the moment when it was first put in. There is absolutely no difference between the air within and that without, save that the one is dustless and the other dust-laden. Clinch the experiment thus. Open the door of your chamber and allow the dust to enter it. In three days afterwards you have every vessel within the chamber swarming with bacteria, and in a state of active putrefaction. Here, also, the inference is quite as certain as in the case of the powder sown in your garden. Multiply your proofs by building fifty chambers instead of one, and by employing every imaginable infusion of wild animals and tame; of flesh, fish, fowl, and viscera; of vegetables of the most various kinds. If in all these cases you find the dust infallibly producing its crop of bacteria, while neither the dustless air nor the nutritive infusion, nor both together, are ever able to produce this crop, your conclusion is simply irresistible that the dust of the air contains the germs of the crop which has appeared in your infusions. I repeat there is no inference. of experimental science more certain than this one. In the presence of such facts, to use the words of a paper lately published in the Philosophical Transactions,' it would be simply monstrous to affirm that these swarming crops of bacteria are spontaneously generated.""

In a former chapter I stated that there is no reliable evidence that "spontaneous generation" now exists, and that there is no credible evidence that any life now is produced except from antecedent life. That completes one step. From analogy we may infer that if the doctrine of "spontaneous

generation" is false now probably it was always so; and that the laws of nature as regards the production of life have never changed since they were first instituted.

Life only from antecedent life is the present law. But this does not inform us whence life originally came. There must have been a beginning of terrestrial life. But the great fountain of life may have had no beginning. There must have been during past eternity a time or point when life could not be derived from antecedent life. It seems that there must have been a first life, and nothing can be before the first.

Nothing now occurs without an antecedent cause. But there must have been a point or time when there could not be an antecedent cause; and thus we seem to be again forced back upon a self-existing cause, or "cause of causes." It seems to me that all life had its origin in the great first life. Here we have to deal with original causes, concerning which it is said that we can know nothing.

It is true that the human mind cannot comprehend original causes, but it can, in a measure, understand the force of the declaration made to Moses: "I am that I am." And until some man can show a cause for the origin of life which is more likely to be true, we must look to the

great "I Am" as the fountain from which all terrestrial life came.

The Duke of Argyll, quoted before (p. 272, "Reign of Law"), says: "It is the great mystery of our being that we have powers impelling us to ask such questions on the history of Creation, when we have no powers enabling us to solve them. Ideas and faint suggestions of reply are ever passing across the outer limits of the Mind, as meteors pass across the margin of the atmosphere; but we endeavor in vain to grasp or understand them. The faculties both of reason

and of imagination fall back with a sense of impotence upon some favorite phrase some form of words built up out of the materials of analogy, and out of the experience of a Mind, which, being finite, is not creative. We beat against the bars in vain. The only real rest is in the confession of ignorance, and the confession, too, that all ultimate physical Truth is beyond the reach of Science."

And emphatically there is no place where we intellectually "beat against the bars in vain" with greater certainty than with the question, "Whence is life?" unless we are willing to refer its origin to the Great First, or Self-existent Life.

INCREASING SIZE OF THE BRAIN.

235

CHAPTER X.

DEVELOPMENT OF LIFE.

THE questions already discussed lead to further inquiries concerning inherited traits of character and the increased development of the brain during past ages.

Where shall we find a limit to the increasing size of the brain and the consequent enlargement of intellectual capacities?

The brains of vertebrate animals have been increasing in size and activity for many thousand years. The average European human brain of the males is now larger than it was one hundred years ago.

Prof. Marsh, in his lecture on "Vertebrate Life in America," shows that there was a general increase of the size of brains as long ago as the Tertiary period. On p. 48, he writes: "The real progress of mammalian life in America, from the beginning of the Tertiary to the present, is well illustrated by the Brain-growth, in which we have the key to many other changes.

"The earliest known Tertiary mammals all had very small brains, and in some forms this organ was proportionally less than in certain Reptiles. There was a gradual increase in the size of the brain during this period, and it is interesting to find that this growth was mainly confined to the cerebral hemispheres, or higher portion of the brain. In most groups of mammals, the brain has gradually become more convoluted, and thus increased in quality, as well as