This section of the book is from the "Stories of Animal Sagacity" book, by William Henry Giles Kingston.
I have given several instances of friendship existing between horses and dogs.
A fine hunter had formed a friendship with a handsome greyhound which slept in the stable with him, and generally accompanied him when taken out for exercise. When the greyhound accompanied his master in his walks, the horse would look over his shoulder, and neigh in a manner which plainly said, Let me go also; and when the dog returned, he was received with an unmistakable neigh of welcome. He would lick the horse’s nose, and in return the horse would scratch his back with his teeth.
On one occasion the groom had, as usual, taken out the horse for exercise, followed by the greyhound, when a savage dog attacked the latter and bore him to the ground. The horse, seeing this, threw back his ears, and, breaking from the groom, rushed at the strange dog which was attacking his friend, seized him by the back with his teeth, speedily making him quit his hold, and shook him till a piece of his skin gave way. The offender, getting on his feet, scampered off, glad to escape from a foe who could punish him so severely.