From Horace Porter's Campaigning with Grant, pp. 330-1:
"General Ingalls had just returned from a trip to Washington, and brought with him an English spotted coachdog, which followed him everywhere through camp, and attracted no end of attention. A dog of any kind was rather an unusual sight in an army in the field, and an animal of the peculiar marks and aristocratic bearing of Ingalls's companion excited wide-spread remark. Every time the dog came to headquarters, General Grant was certain to comment upon the animal, and perpetrate some good-natured joke at the expense of his classmate. The dog followed the usual canine custom, and expressed his feelings by an agitation of his caudal appendage. To describe his actions astronomically, it may be said that he indicated anger by imparting to his tail a series of longitudinal vibrations, and pleasure by giving it a gentle 'motion in azimuth' — familiarly known as a wag. One evening, as the general was sitting in front of his quarters, Ingalls came up to have a chat with him, and was followed by the dog, which sat down in the usual place at its master's feet. The animal squatted upon its hind quarters, licked its chops, pricked up its ears, and looked first at one officer and then at the other, as if to say: 'I am General Ingalls's dog; whose pup are you?' In the course of his remarks General Grant took a look at the animal, and said: 'Well, Ingalls, what are your real intentions in regard to that dog? Do you expect to take it into Richmond with you?' Ingalls, who was noted for his dry humor, replied with mock seriousness and an air of extreme patience: 'I hope to; it is said to come from a long-lived breed.' This retort, coupled with the comical attitude of the dog at the time, turned the laugh upon the general, who joined heartily in the merriment, and seemed to enjoy the joke as much as any of the party."