His behaviour was in many ways more simian than canine. The lack of hands was a handicap against which he reacted with a dogged will to triumph over disability.

Thomas judged that his weakness in construction was due not only to handlessness but to a crudity of vision which is normal in dogs. Long after infancy he was unable to distinguish between visual forms which Plaxy would never confuse. For instance, it took him far longer than Plaxy to distinguish between string neatly tied up in little bundles and the obscure tangle which, at Garth as in so many homes, composed the general content of the string-bag. Again, for Sirius, rather fat ovals were no different from circles, podgy oblongs were the same as squares, pentagons were mistaken for hexagons, angles of sixty degrees were much the same as right angles. Consequently in building with toy bricks he was apt to make mistakes which called forth derision from Plaxy. Later in life he corrected this disability to some extent by careful training, but his perception of form remained to the end very sketchy.

In early days he did not suspect his inferiority in vision. All his failures in construction were put down to lack of hands. There was indeed a grave danger that his handlessness would so obsess him that his mind would be warped, particularly during a phase when the infant Plaxy was apt to laugh at his helplessness. A little later she was brought to realize that poor Sirius should not be ragged for his misfortune, but helped whenever possible. Then began a remarkable relationship in which Plaxy's hands were held almost as common property, like the toys. Sirius was always running to ask Plaxy to do things he could not manage himself, such as opening boxes and winding up clock-work toys. Sirius himself began to develop a surprising "manual" dexterity, combining the use of fore-paws and teeth; but many operations were for ever beyond him. Throughout his life he was unable to tie a knot in a piece of cotton, though there came a time when he could manage to do so in a rope or stout cord.

Plaxy was the first to show signs of understanding speech, but Sirius was not far behind. When she began to talk, he often made peculiar little noises which, it seemed, were meant to be imitations of human words. His failure to make himself understood often caused him bitter distress. He would stand with his tail between his legs miserably whining. Plaxy was the first to interpret his desperate efforts at communication, but Elizabeth in time found herself understanding; and little by little she grew able to equate each of the puppy's grunts and whines with some particular elementary sound of human speech. Like Plaxy, Sirius began with a very simple baby-language of monosyllables. Little by little this grew into a canine, or super-canine, equivalent of educated English. So alien were his vocal organs to speech, that even when he had perfected the art no outsider would suspect his strange noises of being any human language at all. Yet he had his own equivalent of every vocal sound. Some of his consonants were difficult to distinguish from one another, but Elizabeth and Plaxy and the rest of the family came to understand him as easily as they understood each other. I described his speech as composed of whimpers and grunts and growls. This perhaps maligns it, though essentially true. He spoke with a notable gentleness and precision, and there was a fluid, musical quality in his voice.

Thomas was, of course, immensely elated by the dog's development of true speech, for this was a sure sign of the fully human degree of intelligence. The baby chimpanzee that was brought up with a human baby kept level with its foster-sister until the little girl began to talk, but then dropped behind; for the ape never showed any sign of using words.

Thomas determined to have a permanent record of the dog's speech. He bought the necessary apparatus for making gramophone discs, and reproduced conversations between Sirius and Plaxy. He allowed no one to hear these records except the family and his two most intimate colleagues, Professor McAlister and Dr. Billing, who were influential in procuring funds for the research, and knew that Thomas's secret ambition soared far above the production of super-sheep-dogs.