"Look at this," he breathed reverently; "Six times I tried to isolate the secretion of the Neville gland. Each time I failed, but the seventh time I did it. Can you imagine what this drop of fluid will do, Gilmour?"

"No," said Gilmour, visibly impressed by the old man's emotions.

"No, you couldn't, young man; it is beyond ordinary imagination. After isolating the secretion, it was easy for me to prepare this serum-a mixture that will neutralize it."

Neville stopped and took a deep breath; his face shone with triumph and he seemed to grow three inches. "Inject this serum into a female and it will neutralize the secretion of the predominant sex. The switch is turned over. Freed from the tyrant, the seedlings of the dormant sex will quickly stir to life. Look at it, Gilmour!"

He put the phial on the desk, and stood looking at it in an attitude of worship. "The Seventh Serum," he whispered. "A drop in the blood stream and in three or four days it will completely change a woman to a man-both physically and mentally."

It was his last sentence that confirmed Arnold's suspicions. At last Neville's brilliant mind was beginning to fail!

"Good Lord, that's rather hard to believe, Professor," he said skeptically, and was immediately sorry that he had been so tactless.

"Hard to believe, but nevertheless quite true," answered Neville coldly. He returned the phial to the drawer in silence, and Gilmour knew that his remark had finished the discussion. Neville was annoyed; he disliked unbelievers and men who questioned his learning. As Gilmour watched the professor fiddling huffily at his desk, he decided to get back to business. He had wasted enough time, and be had already upset the professor; to ruffle him a bit more would not do much barm.

So he screwed up his courage and with all the defiant aggressiveness of youth, he informed Neville of his altered position and his intention of marrying Jeanette as soon as possible. Then he stood back to await the outburst. CLICK HERE TO GO TO CHAPTER IV