To revert to the function of the testes, we may say that during these various stages of sexual stimulation and excitement the testes are actively secreting thousands upon thousands of nascent spermatozoa, which being released, are hurried along, partly by their own flagellate movements and partly by the action of the cilia in the ducts of the epididymis and the peristaltic contractions of the vas deferens--hurried along the vas to the ampulla. If the period of sexual excitement extends over fifteen to thirty minutes, the whole duct system from the epididymis to the ampulla becomes gorged with the secreted testicular product. This secretion consists of active motile spermatozoa, of spermatic granules and of mucus. The latter is secreted by the ducts of the epididymis and the vas deferens, the testicle itself furnishing only spermatozoa, spermatic granules and a small amount of liquid, just sufficient in quantity to float the spermatozoa out of the testes into the ducts. At the moment of sexual orgasm occurs what is known as, the emission of semen. In this act the whole contents of the ampulla, vas deferens and ducts of the epididymis, the contents of the seminal vesicles, and the contents of the ducts of the prostate gland are all poured out by spasmotic muscular contractions into the urethra and by contraction of the walls of the urethra, ejected from that tube through the mouth of the urethra. Thus, in the act of emission, there is an intimate mixing together of the three contributions to the semen, i.e., the _testicular, vesicular and prostatic_. _Sub-conscious Sexual Stimulation._--Sub-conscious sexual stimulation is not accompanied by erection or any mental or physical manifestation of sexual excitement.