He retired in 1911 since, unable to see, he was totally reliant on his memory to give lectures and he felt that his memory was beginning to fail.
Siya ay nagretiro mula noong 1911, hindi na makita, siya ay ganap na tiwala sa kanyang memorya upang magbigay ng lektura at siya nadama na kanyang memorya ay nagsisimula sa mabibigo.