Proceeding in this manner, it seems to me impossible to refuse to allow animals a certain amount of consciousness of their actions. Doubtless, they do not form such an exact estimate of them, as even an illiterate man can do. But we may be very certain that when a cat is trying to catch sparrows on level ground, and creeps along the hollows, availing herself of every tuft of grass however small, she knows what she is about, just as well as the hunter who glides in a crouching attitude from one bush to another. We may be equally sure that kittens and puppies when they fight, growl and bite without hurting each other, know very well that they are playing and not in earnest. I must here beg permission to relate the remembrance of my struggles with a mastiff of pure breed, and which had attained its full size, remaining, however, very _young in character_. We were very good friends, and often played together. As soon as ever I assumed an attitude of defence before him, he would leap upon me with every appearance of fury, seizing in his mouth the arm which I had used as a shield. He might have marked my arm deeply at the first onset, but he never pressed it in a manner that could inflict the slightest pain. I often seized him by his lower jaw with my hand, but he never used his teeth so as to bite me. And yet the next moment the same teeth would indent a piece of wood, I tried to tear away from them. This animal evidently knew what it was doing when it feigned the passion precisely _opposite_ to that which it really felt; when, even in the excitement of play, it retained sufficient mastery over its movements to avoid hurting me. In reality it _played a part in a comedy_, and we cannot act without being conscious of it. It is useless for me to insist upon many other facts which I could bring forward, and I refer my reader to the works of those naturalists who have studied the question, especially those of F. Cuvier. But the more I reflect upon it, the more is my conviction confirmed that man and animals think and reason in virtue of a faculty which is common to both, and which is only far more developed in the latter than in the former. What I have just said of the intelligence I do not hesitate to say also of language, the highest manifestation of the intelligence. It is true that man alone possesses _speech_, that is to say the _articulate voice_. But two classes of animals possess _voice_. With us it is, again, only a high degree of perfection, nothing radically new. In both cases the sounds, produced by the air which is thrown into vibration by the voluntary movements accorded to the larynx, convey impressions and personal thoughts which are understood by individuals of the same species. The mechanism of the production, the object and the result are fundamentally the same.