<P> The gubernaculum grows into a thick cord . It ends below at the abdominal inguinal ring in a tube of peritoneum, the saccus vaginalis, which protrudes itself down the inguinal canal . By the fifth month the lower part of the gubernaculum still is a thick cord, while the upper part has disappeared . The lower part now consists of a central core of smooth muscle fibers, surrounded by a firm layer of striated muscle elements, connected, behind the peritoneum, with the abdominal wall . </P> <P> As the testes develops, the main portion of the lower end of the gubernaculum is carried, following the skin to which it is attached, to the bottom of this pouch . Other bands are carried to the medial side of the thigh and to the perineum . The tube of peritoneum constituting the saccus vaginalis projects itself downward into the inguinal canal, and emerges at the external inguinal ring, pushing before it a part of the obliquus internus and the aponeurosis of the obliquus externus, which form respectively the cremaster muscle and the external spermatic fascia . The saccus vaginalis forms a gradually elongating pouch, which eventually reaches the bottom of the scrotum, and behind this pouch the testis is drawn by the growth of the body of the fetus, for the gubernaculum does not grow proportionately with the growth of other parts, and therefore the testis, being attached by the gubernaculum to the bottom of the scrotum, is prevented from rising as the body grows, and is instead drawn first into the inguinal canal and eventually into the scrotum . It seems certain also that the gubernacular cord becomes shortened as development proceeds, and this assists in causing the testis to reach the bottom of the scrotum . </P> <P> By the end of the eighth month the testis has reached the scrotum, preceded by the saccus vaginalis, which communicates by its upper extremity with the peritoneal cavity . Just before birth the upper part of the saccus vaginalis, at the internal inguinal ring, usually becomes closed, and this obliteration extends gradually downward to within a short distance of the testis . The process of peritoneum surrounding the testis is now entirely cut off from the general peritoneal cavity and constitutes the tunica vaginalis . </P> <P> If the internal inguinal ring does not close properly, then there is a risk that other contents of the abdominal cavity protrudes through the passageway and cause indirect inguinal hernia . </P>

When does the testes descend from the peritoneal cavity
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