33. EDITORIAL. Jour. of Amer. Med. Assoc., LXXVII, No. 1, 42, July 2, 1921. 34. REYNOLDS, E. Fertility and Sterility. Jour. of Amer. Med. Assoc., LXVII, 1193–1199, October 21, 1916. 35. CARY, W. H. Examination of Semen With Special Reference to Its Gynecological Aspects. Amer. Jour. of Obstetrics and Diseases of Women and Children. LXXIV, No. 4, 1916. 36. WOLF, C. G. L. The Survival of Motility in Mammalian Spermatozoa. Jour. of Physiol. IV, 246, August 3, 1921. 37. BROWN, J. H. The Use of Blood Agar for the Study of Streptococci. Monograph of the Rockefeller Institute for Med. Res., 1919, IX. 38. GARNETT, J. B., and others. The Surgical Treatment of Sterility due to Obstruction at the Epididymis Together with a Study of the Morphology of Human Spermatozoa. Univ. of Penn. Med. Bulletin, March, 1902. 39. REYNOLDS, E. and MACOMBER, D. Defective Diet as a Cause of Sterility. Jour. of Amer. Med. Assoc., LXXVII, 169, July 16, 1921. 40. NOVARRO, P. A. Tissues of the Testicle and Antaminosis. Gazetta degli Ospedali (Milano), 1920, XLI, 424. 41. WILLIAMS, W. L. Observations on Reproduction in a Pure Bred Beef Herd. Cornell Veterinarian. January, 1922. 42. BELL, W. B. Correlation of Function: With Special Reference to the Organs of Internal Secretion and the Reproductive System. Brit. Med. Jour., 1920, 1, 787. 43. BROWN, W. L. The Principles of Internal Secretion. Brit. Med. Jour, 1920, II, 687–691. 44. JUMP. Discussion in Penn. Med. Jour., XXV, 81. 45. BIEDL, A. The Internal Secretory Organs. 46. HEWER, E. E. The Effect of Thymus Feeding on the Activity of the Reproductive Organs of the Rat. Jour. of Physiology, XLVII, 1913–1914, 479. 47. LLOYD-JONES, O. and HAYS, F. A. The Influence of Excessive Sexual Activity of Male Rabbits. 1. On the Properties of the Seminal Discharge. Jour. of Exper. Zoology, 1918, XXV, 463. 48. WILLIAMS, W. L. Improvement of the Reproductive Efficiency of Cattle. North Amer. Veterinarian, III, May, 1922. DESCRIPTION OF PLATES PLATE I. Fig. 1. Diagrammatic sketches showing the development of a spermatozoon from a spermatogonium. Fig. 2. Diagrammatic sketch showing the minute structure of a spermatozoon. The middle piece is made comparatively thick in order to bring out the finer structures. Adapted from Ellenberger. PLATE II. Fig. 3. Testicle of bull, showing extensive degeneration and necrosis. PLATE III. Fig. 4. Inner part of wall of ductus deferens. Normal. × 230. Fig. 5. Same, but showing extensive degeneration and exfoliation of the lining membrane. × 230. PLATE IV.