Charles, the young Army Medical, went down on one patella. His heart (a hollow muscular pump) was driving blood from its ventricles as it had never yet driven it in all its twenty-five years of incessant labour. Further, by flattening the arch of his diaphragm and elevating his ribs and sternum, Charles was increasing the cavity of his thorax and taking in air. Immediately the diaphragm and the sternum and costal cartilages relaxed again the air escaped. The lungs of Charles were doing their work. Fast and yet faster became his breathing. "Mabel," he murmured, "Mabel!" The girl made no movement. Her respiration continued, but no impulse to action reached her nerve-centres. Yet, without an effort on her part, her tissues in one minute produced enough heat to boil one twenty-fourth of a pint of water. "Wonderful!" he whispered hoarsely, probably thinking of this, "you are wonderful." You will not marvel that his voice was gruff when I tell you that the membrane of the larynx was inflamed. Greater men than Charles have become hoarse in such circumstances. Immediately the blood rushed to the capillaries of Mabel's cheeks and her colour deepened. She trembled slightly. "There, that's it!" he cried, gazing rapturously. "What?" she gasped, startled by his passion. "Again that artery below your ear is throbbing, throbbing, and"--his voice rose in despair--"I can never remember the name! Can you?" "Alas," she moaned, "I do not know it! Oh, Charles, there is something I must tell you at once." "What is it?" he cried with sudden fear. "What is it?" "Why, I--I----Oh, I do not know how to say it. Charles, you will never forgive me!" "What is it, dearest? Tell me--you can trust me. The medical profession----" "Well, then, I tried to bandage little Johnny's foot yesterday, and--and----" "Calm yourself, dear. And----?" "I tied a 'granny' knot. Oh, Charles, _don't_ be angry. I _know_ it ought to have been a 'reef'!" He looked about him dully, like a man stunned. "Charles," she moaned, "listen! After all, I put it on the wrong foot." He started violently. "Mabel," he cried, "you are sure? Then I will not let you go. Had you tied that 'granny' knot on the right foot, I--we--as an R.A.M.C. man, I----" She clung to him sobbingly. "Charles, oh Charles," she panted, "you have proved it to me. You love me! (Is my heart throbbing now?) You love me and it will break for joy!" The phalanges and the metacarpal bones of her left hand clicked together as if in sympathy as she flung it to her side. Again her cerebrum flashed its joyful message, so that she repeated, "My heart!" At the word Charles, the R.A.M.C. man, rose from his patella and placed his hands firmly on his femur bones. His whole bearing had changed.