In certain parts of the American tropics there is found a rich, grey moss growing in great profusion in certain localities and on certain kinds of trees. It is not confined to any certain level, but thrives best on the lowest elevations. Under favourable conditions it will grow at altitudes far above the surrounding swamps. The character and quantity, however, are measured by the altitude at which it grows. It is an aerial plant, and may be detached from the boughs of one tree and transplanted upon those of another. It may be taken with safety for a great distance so long as an atmosphere is supplied to it that is suited to its nature; but when removed from its normal conditions and placed in a purer air it begins to languish and soon dies. If it be returned in time, however, to its former place or one of like character it will revive and continue to grow. What element this plant extracts from the impure air is a matter of doubt; but it cannot be carbonic acid gas which is the chief food of plants, nor it cannot be any form of nitrogen; and it is well known that the plant cannot long survive in a pure atmosphere. Whatever the ingredient extracted may be, it is certain that it is one that is deadly to human life, and one which other plants refuse. Moisture and heat alone cannot account for it. We have another striking instance in the eucalyptus, which lives upon the poison of the air around it. There are many other cases in vegetable life, and while the animal is a higher organism than the plant, there are certain laws of life that obtain in both kingdoms which are the same in principle. Between the case of the gorilla and that of the plant there is some analogy. It may not be the same element that sustains them both, but it is possible that the very microbes which germinate disease and prove fatal to man sustain the life of the ape in the prime of health. The poison which destroys life in man preserves it in the ape. The chimpanzee is distributed over a much greater range, and is capable of undergoing a much greater degree of change in food and temperature. The history of these apes in captivity shows that the chimpanzee lives much longer in that state and requires much less care. From my own observation I assert that all of these apes can undergo a greater range of temperature than they can of humidity. This appears to be one of the essential things to the life of a gorilla, and one fatal mistake made in treating him is furnishing him with a dry, warm atmosphere, and depriving him of the poison contained in the malarious air in which he spends his entire life. Both of these apes need humidity. The chimpanzee will live longer than a gorilla in a dry air, but neither of them can long survive it, and it would appear that a salt atmosphere is best for the gorilla.