628 Proceedings of the Royal Irish Academy. 



ing the latter into two pillars. These nerves sometimes pierce the crus 

 medium. The v. azygos or hemiazygos may pass through the inter- 

 val between the middle and external crura on the corresponding 

 side, and either — hardly ever both — may pass through the aortic 

 opening. 



The hiatus aorticus transmitted the major splanchnic nerve in 

 three instances; the corresponding nerve of the right side passed 

 through the same opening in one case, while that of the left side did 

 so in two of the thirty-six bodies. The n. splanchnicus minor of the 

 right side pierced the crus internum in one instance. The v. azygos 

 major passed through the aortic orifice in two of the bodies. The 

 hemiazygos vein passed through the interval between the middle and 

 external crura in the same subjects. 



The occurrence of erratic muscular slips was noted in several of 

 these specimens. In two cases a well-defined muscular bundle of an 

 inch in breadth arose from the back of the sheath of the rectus 

 abdominis, close to the xiphoid appendix. A narrow bundle of mus- 

 cular fibres, stretching antero-posteriorly on the left leaflet of the cor- 

 diform tendon, was present in one case, and I have met with the same 

 anomaly in two other instances. A muscular band, passing from the 

 under surface of the tendon in front and to the left of the oesophageal 

 orifice, and adherent to the upper surface of the Kver at its other 

 extremity, forming a m. hepatico-diaphragmaticus, was present in one 

 of the bodies. A distinct muscular band, passing in front of the aortic 

 orifice, was present in five cases. The other variations noted were 

 chiefly of the extent of the costal attachments. 



Oiliqutis abdominis externus. — The variations of this muscle I have 

 also tabulated in thirty-six cases, besides noting other anomalies 

 which came under my notice.- The digitations of origin have been 

 found by me, as by most other observers, to vary usually from six to 

 nine, but in one instance no less than ten were enumerated, the eight 

 lower ribs giving attachment, and the seventh and eight ribs having 

 each two digitations. In two cases the twelfth rib did not give origin 

 to any of the muscular fibres, and this variety I have also noted in 

 five other instances (not included in the number specially examined). 



Some of the fibres were twice found continuous with those of the 

 serratus anticus magnus ; in both cases these fibres were connected 

 with the ninth rib. The posterior fibres, which, descending less 

 obliquely than the others, pass to the iliac crest, present consider- 

 able variations in the extent of the osseous tract to which they are 

 attached on the ilium. This I have found to vary from one-third to 

 two-thirds of the length of the crest. In one instance (and in four 

 other cases noted from time to time) the iliac origin of the latissimus 

 dorsi came into absolute contact with the posterior edge of the oblique 

 muscle at its attachment to the bone, so that the triangle of Petit did 

 not exist. This was found in all the cases in very muscular subjects. 

 The degree of adhesion of the aponeurosis to the linea semilunaris 

 SpigeUi I have found to vary very considerably : in one case it could 



