PLATE LXI1I.-LXIV. 

 DEEP VIEW OF THE FRONT OF THE ABDOMINAL WALL. 



This plate represents a deeper dissection on the same body as the previous one. ( )n 

 the right side, the internal oblique has been divi.l. <i external to the linea semilunaris to 

 expose the transversalis ; while on the left the anterior portion of the sheath of the rerun 

 has been stripped off to expose it and the pyrainidulis, the oblique and transversalis 

 muscles being cut away to expose the fascia transversalis. 



The pyramidalis is specially developed in those animals which possess a marsupial 

 bone. 



It will be noticed that the arching fibres of the transversalis springing from Poupart's 

 ligament and passing inwards to join those of the internal oblique (forming the con- 

 joined tendon), leave an oval space which is guarded only by the transversalis fascia. 

 This space is crossed by the deep epigastric artery, and thus divided into two (i) an 

 external part, the internal abdominal ring ; and (ii) an internal, the lower portion of 

 Hesselbach's triangle : the latter is again crossed and strengthened by the obliterated 

 hypogastric artery. Through the internal ring the cord or round ligament passes, and 

 the oblique form of inguinal hernia descends when present, following the course of tin- 

 cord along the inguinal canal, and issuing at the external abdominal ring. It would 

 thus have the following coverings : 1. Peritoneum and subperitoneal tissue ; 2. In- 

 fundibuliform process of the fascia transversalis ; 8. Cremasteric fascia ; 4. Inter- 

 columnar fascia; 6. Subcutaneous tissue and skin. 



It must be remembered that the testicle in its descent pushes before it a process of 

 peritoneum, the lower part of which remains as the tunica vaginalis, while the upper 

 portion usually becomes obliterated. Should the whole of this process remain 

 unobliterated so that the tunica vaginalis communicates with the peritoneal cavity, 

 the bowel may have to overcome only a slight constriction at the internal ring to 

 at once slip into the canal and descend into the tunica vaginalis, lying in front of 

 the testis a congenital hernia ; or should the opening be so small that only the 

 peritoneal fluid- can drain into it, this fluid collects in the tunica vaginalis and forms a 

 congenital hydrocele. Again, the tunica vaginalis may be cut off from the upper part of 

 the process, and this process remain unobliterated : then the gut may descend into it and 

 form a hernia into the funicular pouch of the peritoneum, or an infantile hernia. 



\\ hen the gut descends through the lower part of Hesselbach's triangle the direct 

 form it may pass on either side of the obliterated hypogastric. If to the outer side thu 

 most common form between it and the deep epigastric artery it would receive the same 

 coverings as in the oblique form, save that it would push the main part of the fascia 

 transversalis as a covering in front of it instead of entering the infundibuliform pro- 

 longation of that fascia through the internal ring. The rarer form is when the gut 

 comes through to the inner side of the obliterated hypogastric artery, and has to push 

 before it or separate the fibres of the conjoined tendon which here strengthens the wall. 

 It thus breaks through the wall opposite the external ring out of which it passes, and it 

 has as coverings: 1. Peritoneum and subperitoneal tissue; 2. Fascia transversalis; 

 8. Conjoined tendon ; 4. Intercoluimiar fascia ; 5. Skin and subcutaneous tissue. 



s 



