Animal intelligence varies in quantity and quality as much as animals vary in size. Idiots, maniacs and sleeping persons are the only classes of human beings who are devoid of intelligence and reasoning power. Idiots and maniacs also are often devoid of the common animal _instinct_ that ordinarily promotes self- preservation from fire, water and high places. A heavily sleeping person is often so sodden in slumber that his senses of smell and hearing are temporarily dead; and many a sleeping man has been asphyxiated by gas or smoke, or burned to death, because his deadened senses failed to arouse him at the critical moment. (This dangerous condition of mind can be cured by efforts of the will, exercised prior to sleep, through a determination resolutely to arouse and investigate every unusual sensation that registers "danger" on any one of the senses.) The normal individual sleeps with a subconscious and sensitive mind, from which thought and reason have not been entirely eliminated. Every act of a man or animal, vertebrate or invertebrate, is based upon either _reason_ or _hereditary instinct._ It is a mistake to assume that because an organism is small it necessarily has no "mind," and none of the propelling impulse that we call thought. The largest whale may have less intelligence and constructive reasoning than a trap-door spider, a bee or an ant. To deny this is to deny the evidence of one's senses. A MEASURE FOR ANIMAL INTELLIGENCE. The intelligence of an animal may be estimated by taking into account, separately, its mental qualities, about as follows: 1. General knowledge of surrounding conditions. 2. Powers of independent observation and reasoning. 3. Memory. 4. Comprehension under tuition. 5. Accuracy in the execution of man's orders. Closely allied to these are the _moral qualities_ which go to make up an animal's temperament and disposition, about as follows: 1. Amiability, which guarantees security to its associates. 2. Patience, or submission to discipline and training. 3. Courage, which gives self-confidence and steadiness. 4. A disposition to obedience, with cheerfulness. All normal vertebrate animals exercise their intelligence in accordance with their own rules of logic. Had they not been able to do so, it is reasonable to suppose that they could never have developed into vertebrates, reaching even up to man himself. According to the laws of logic, this proposition is no more open to doubt or dispute than is the existence of the Grand Canyon of the Colorado. But few persons have seen the Canyon, and far fewer ever have proven its existence by descending to its bottom; but none the less Reason admonishes all of us that the great chasm exists, and is not a debatable question.