Text-book of the embryology of man and mammals / by Oscar Hertwig ; translated from the third German edition by Edward L. Mark.

Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of the embryology of man and mammals / by Oscar Hertwig ; translated from the third German edition by Edward L. Mark. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    419/704 (page 391)
    attention wa« dii-ected to the non-striate muscle-fibres contained m it, or a shortening of the connective-tissue cord by gradual shrinkage was assumed. But it is impossible for this very important change in position to have taken place in that manner. One therefore rightly seeks to explain the agency of the Ugament in another way, without assuming an active shortening or a traction exercised by muscular action. We have to do here simply with processes of unequal growth. When, out of several organs originally lying beside one another in the same region of the body, certain ones in later months of embryonic life increase in size less, while others, on the contrary, grow extraordinarily in length, the natural consequence is that the more rapidly growing parts are shoved past those that grow Fig. 224.—Two diagrams to illustrate the descensus and the formation of the envelopes of the testis. A, The testis lies in the vicinity of the inner abdominal ring. B, The testis has entered the scrotum. 1, Skin of the abdomen; 1', scrotum mth tunica dartos; 2, superficial abdominal fascia; 2', Cooper's fascia; 3, muscle-layer and fascia transversa abdominis; 3', tunica vaginalis communis with cremaster; 4, peritoneum ; 4', parietal layer of the tunica vaginalis proijria ; 4, peritoneal investment of the testis or visceral layer of the tunica vaginalis propria. if. Inguinal or abdominal ring; 7t, testis ; si, vaa deferens. more slowly. If, now, in the present case the skeletal parts and their accompanying muscles in the lumbar and pelvic regions become elongated, while the Hunterian hgament does not grow and there- fore remains short, the latter necessarily—because one of its ends is attached to the skin of the inguinal region and the other to the testis—draws down the testis as the movable part; it draws the testis at first gradually into the cavity of the false pelvis, and finally, when the other parts have become still larger, when at the same time the abdominal wall has become much thicker, into the vicinity of the inner abdominal ring (fig. 223). The testis migrates still farther in consequence of a second process, which begins even in the second month. For there is formed at the place where Hunter's ligament travei-ses the wall of the abdomen an evaginatiou of the peritoneum, the processios vaginalis po'ilonei