This passage takes on significance when it is contrasted with an earlier one. In the beginning of the story, Kino arises at dawn as another day begins. He steps outside to watch the sunrise, which is quite beautiful on the Gulf of Mexico. Alone on the beach, hears Juana inside preparing their breakfast while their baby sleeps. At this point, Kino is joined by a dog:
A thin, timid dog came close and, at a soft word from Kino, curled up, arranged its tail neatly over its feet, and laid its chin delicately on the pile [of sand]. It was a black dog with yellow-gold spots where its eyebrows should have been. It was a morning like other mornings and yet perfect among mornings.
Thus in the beginning of the story, Kino's life is beautiful and peaceful; he lives in harmony with the world around him.
Kino encounters the dog a second time in Part III of the story. At this time, Coyotito's illness has forced Kino and Juana away from their home and into the world at large. Kino has found the great pearl with its promises of riches beyond his previous imaginings. Kino is caught up in a new world of possibilities; his very identity has changed in the village. He is no longer Kino; he is the one who possesses The Pearl of the World as news his discovery spreads throughout the village and beyond. Alone on his beach at night, after all the neighbors have left, the dog approaches Kino again:
The thin dog came to him and threshed itself in greeting like a windblown flag, and Kino looked down at it and didn't see it. He had broken through the horizons into a cold and lonely outside. He felt alone and unprotected, and scraping crickets and shrilling tree frogs and croaking toads seemed to be carrying the melody of evil. Kino shivered a little . . . .
Kino's reaction to the dog, who greeted him as a friend, emphasizes to what extent Kino's world has changed. The warmth and harmony of his life has been destroyed, and he finds himself living in fear and isolation.