INGUINAL HERNIA Etiology and testes, or male genital glands, develop in pairs from the primitive structure of the Wolffian bodies behind the peritoneum on a level with the third lumbar vertebra (see Sketch of development). Cell masses soon begin to form, extending from this site to the later location of the testes outside of the inguinal canal, the testes gradually sinking into these cell masses in the course of growth. The cell masses indicate the path, as it were, which the testes have taken at various stages of growth in their fetal development. By the disap pearance of their proximal part, these cells, known as the gubernaculum Hunteri, rapidly disappear, leaving but the few remnants that are found later (Fig. 36).
In the region of the internal inguinal ring the peritoneum forms a cul-de-sac which is swept along by the testis and becomes deepened, forming the processus vaginalis. Apparently, therefore, the testis lies embedded in the invagination, or, perhaps, in one of its outer folds, although the walls of both are in close connection.
The migration through the inguinal canal commences in the sixth month and is completed at the time of birth, the left testis being already in the scrotum, while the right one usually occupies a higher position.
Accompanying the peritoneum, the other abdominal membranes and layers are swept along. The fascia transversalis will become the tunics vaginalis communis, and the muscle fibres of the obliquus interims will form the cremaster muscle in the scrotum. The continuation of the superficial abdominal fascia invests the structures of the scrotum as the dartos.
The peritoneal process is normally obliterated at the time of birth with the exception of its lowest part which permanently envelops the testis as tunica vaginalis. The obliteration occurs in various places at various periods, a fact which is of special importance for the topo graphical anatomy of the development of herniae and hydrocele. (See Hydroecle, Fig. 3S.) If the process of development has taken a normal course, the peri toneum will pass smoothly over the internal inguinal ring; only a small groove, the fovea inguinalis lateralis, points to the process of develop ment which has taken place.
Similar conditions prevail in the female. The ovary, however, remains permanently in the true pelvis. The gubernaculum testis persists as round ligament, while the existing proeessus vaginalis is soon closed (diverticulum; see Canalis Nuckii).
Thus, in every male foetus we find normally in the seventh month an open processus vaginalis, a condition which persists in many species of mammals where the intestinal loops will not readily enter, even less easily than in the normal foetus. The explanation is that the hernial rings are closed by muscles and that only a pathological change in the width of the rings or in the power of the sphincter, or a considerably increased internal pressure, will allow the intestines to pass through. The external inguinal opening in the normal newborn, whether slitlike or oval, will easily admit the little finger, while larger circular or tri angular openings arc of pathological significance. The muscular barrier is formed by the two oblique abdominal muscles, between which the inguinal canal is forced.
However, in about 50 per cent. of newborn infants the processus vaginalis is still open at the time of birth. This condition may change to normal during the first weeks, but it may persist for life often without causing any particular disturbance.
Pathological the intestines or other abdominal con tents can pass into the preformed hernial sac, there exists an inguinal hernia which may be regarded as congenital. If the intestinal loop enters the open inguinal canal external to the plies epigastriea, it is called oblique inguinal hernia, as distinguished from direct inguinal hernia which may originate at a second weak portion of the abdominal wall, namely, the outer inguinal opening internal to the plica epigastrica.