The irruption of the London "Yahoos" had taken place, and they were pouring in, headed by a fierce-looking, crop-eared, bullet-headed ruffian, and the fight began. Medical students can fight; and upon this occasion they used their fists scientifically and well; but the odds were against them. The mob swept on, and the big ruffian and a dozen companions made a dash over the seats, treating them as they would those of the gallery of a theatre on a night when they wished to express their displeasure. Before Horace North realised the fact, they were upon the group by where the operating table had stood, and close to another table upon which were bottles, glasses, basins, sponges, and a pestle and mortar. The young doctor was borne back as the yell--the war-cry, "Yah! Body-snatchers!"--once more arose, and as he struggled with one scoundrel who tried to take vengeance upon him by stealing his watch, he saw the grey-headed old surgeon struck down by the bullet-headed, butcher-like ruffian who led the gang; and the fellow was about to follow up his attack by performing a war-dance upon the defenceless old man. He had not time, for Horace North literally flung himself upon the savage and drove him from his prey, but only to be grasped in turn by one whose greatest pleasure was destruction, and whose unpleasant mouth expanded into a satisfied grin as he bore back the body of his weaker adversary, and with it a good deal of the future of Mary and Leo Salis linked in with that of half the village of Duke's Hampton. "Ah, would yer! it's my turn now." The vengeance of his class against what he called a "swell." CHAPTER THREE. SCIENCE AT WORK. Horace North was more of the student than the athlete, and he felt the blood rushing to his head--a strange sensation of vertigo which he could have aptly described in writing, and thoroughly expressed, with all due detail, the action going on by the compression of certain veins and an artery. But for a few moments, in the _melee_, he could do nothing to free himself of the savage grip, which threatened to injure him for life, if it did not quite destroy. But science is a fine backer of brute force. A man with little muscle is the equal of a giant when both are armed with sword or pistol; and could Horace North have brought his science to bear in the shape of galvanism or some anaesthetic, he would have had the burly giant at his mercy instead of rapidly losing his senses. Galvanism was, however, not at hand, the opportunity to administer a dose of ether or chloroform was also wanting, and as one of the young doctor's hands vainly grasped the ruffian's sinewy wrist, the other fell nearly nerveless upon the table against which he was borne. Here, fortunately, he found the much-needed help of science in the shape of a pestle of marble comfortably reposing in its native mortar.