27 



sternum. Tlie M. obliq. ext. (4j |)asses in front of tlie M. rectus, the 

 Meinhr. iiiterni. (3), tlie M. obliq. int. (2) and the M. transv. (1) 

 form the [)Osterior lamella of the slienth. These relations exist howevei 

 onl}' in the cranial '/„ part of the sheath ; in the caudal iiart the 

 M. obliq. ext. remains before the M. reetn.s, the M. oblicj. int. and 

 the M. transv. behind it, but the Membr. interm. passes at the lateral 

 edge of the M, rectus into the perimysium externum of this muscle, 

 (tig. 1/'). These relations continue to exist till the synq)hysis. (Com- 

 pare the sagittal section, (ig. Jr). 



With an Ateles hi/po.midhus examined In mc the relation of the 

 M. obi. iiil. and Membr. intermedia to the M. rectus was dilferent 

 from that wiih Ateles paiiisciis. The M. obli(|. ext. passes entirely 

 before, the M. transv. entirely behind the M. rectus; the relations 

 the Membr. interm. and the M. obliq. int. bear to the M. rectus are 

 however not the same in all the parts of their course; in the cranial 

 part both run behind the M. rectus (tig. 2a). About 6 cm. caudally 

 from the inferior edge of the sternum (the total distance sternum- 

 symphysis amounts to 12 cm.) the membrane splits into two layers 

 one of which is passing before, the other behind ihe M. rectus. 

 The M. oblic|. int. continues to send its aponeurosis into the posterior 

 lamella of the sheath (fig. 1h). 2'/, em. cranially from the synq)hysis 

 the two layers of the membrane terminate almost simultaneously ; at 

 the same time the M. obliq. int. changes its relation to the M. rectus: 

 from here its aponeurosis divides itself into two layers, which include 

 the M. rectus (vide fig. 2c). Fig. '2(1 gixes an illuslralion (if these 

 different anatomical relations. 



The third tig. relates to the rectal sheath of Cclnis Cuiuiciniis. 

 The M. obliq. ext. passes entirely before, the M. transv. entirely 

 behind the M. rectus. The Membr. interm. passes in the cranial 

 part, just like the M. obliq. int, behind the M. rectus (fig. 3rt) ; in a 

 caudal direction it splits into two layers, enclosing the M. rectus, 

 the M. obliq. int. does provisionally not change its relation to the 

 M. rectus (fig. 3A). Then the dorsal layer of the membrane disaiipears 

 and tliereupon the membrane passes entirely into Ihe anterior lamella 

 of the sheath (fig. 3c'). A little farther caudally the aponeurosis of 

 the M. obliq. int. splits into two layers (fig. 3(/) ; then the deep layer 

 disappears, so that in the caudal part the posterior lamella of the 

 rectal sheath consists only of the aponeurosis of the 'M. transversus, 

 whilst the other three elements pass in front of the M. rectus 

 (fig. 3(' and 3/'). 



With the condition of the rectal sheath found willi (>/;».< 

 caitiiriiui.s. coi'res[)onds the structure of Ihe shealli of all other 



