If a man has been sterilized by vasectomy, restoration of function and removal of the sterility seems practically always possible. If a ligature has been used, releasing the ligature restores function. Dr. William T. Belfield of Chicago[220] restored function fully by removing the ligature eight weeks after it had been applied. In a letter to me, Dr. Belfield said: "My observation accords with the general experimental and clinical experience that the restoration of the lumen after vasectomy or ligation, or both, is more certain than the lasting occlusion of the vasa by these measures. The perseverance of natural forces in restoring the lumen of the vas--and the success achieved over such obstacles as silk ligatures--is surprising until one reflects upon the natural factors favoring such restoration. In one case I tied a waxed (to avoid cutting through) silk ligature _tightly_ around the sheath of each vas; a specimen examined a month later was devoid of sperms; one six months later contained plenty of them. I cut down upon the ligatures, found them in place and neatly encysted, and removed them. Evidently the pressure from behind had squeezed a passage on at least one side. The gynecologists have learned that ligatures around the Fallopian tubes are apt to cut through, whereupon the tubal lumen is restored, though pressure must be less than in the vas. Even when a piece of the vas has been excised cases of spontaneous restoration have been observed in men and dogs."[221] [220] _Jour. Amer. Med. Assoc._, October 19, 1912. [221] _Belfield, loc. cit._ When the ends of a cut vas are released from cicatricial tissue, these ends may be sutured together; but as the lumen of the vas is extremely small, there is sometimes obliteration by occlusion at the juncture. Christian and Sanderson[222] described a method of preventing this obliteration. A piece of No. 0 twenty-day catgut is inserted three-eighths of an inch into each end of the vas, and these ends are brought together by two catgut sutures, leaving the inserted catgut in the canal. The ends heal together and the catgut in the canal is absorbed. This method has been used successfully to join the cut end of a Fallopian tube. [222] _Jour. Amer. Med. Assoc._, December 13, 1913. Gemelli[223] did vasectomy on eleven dogs and seven cats; about six months later he reunited the cut ends, and on dissection found restoration perfect, anatomically and functionally, in the eighteen animals. The vas deferens in these animals is smaller than in man; and therefore offers greater difficulty in the suturing. He used no inserted catgut, but told me he employed the method Carrel applies in joining cut arteries. In one case, where the dissection was broad, he successfully inserted a piece of a vas taken from another animal. Whether there is occlusion or not after end-to-end suturing depends largely on the skill of the surgeon. [223] _La Scuola Cattolica_, November, 1911.