The expression ‘when this excuse failed him’ suggests that the

A wolf, seeing a lamb drinking from a river, wanted to find a pretext for devouring him, He stood higher up the stream and accused the lamb of muddying the water so that he could not drink. The lamb said that he drank only the tip of his tongue and that in any case he was standing lower down the river, and could not possible disturb the water higher When this excuse failed him, the wolf said: ‘Well, last year you insulted my father.’ “I wasn’t even born then replied the lamb. ‘You are good at finding answer’ said the wolf, ‘but what do you mean by taking up so much of the path where I am walking?’ The lamb, frightened at the wolf’s angry tone and terrible aspect, told him, with all due submission, that he could not conceive how his walking on such a wide path could occasion him any inconvenience. ‘What!’ exclaimed the wolf, seemingly in great anger and indignation. ‘You are as impudent as your father who seized me by the throat last year and caused me to be kept in a cage for three months’. ‘If you will believe me,’ said the lamb, ‘my parents are poor simple creatures who live entirely by green stuff, we are none of us hunters of your species.’ Ah! I see it’s no use talking to you,’ said the wolf, drawing up close to him. ‘it runs in the blood of your family to hate us wolves, and therefore,as we have come so conveniently together, I’ll just pay off a few of your forefathers scores before we part.’ So saying, he leapt at the lamb from behind and garotted him. Adapted from Bennet. C.H(1978)