^1 



invsnnii cxlcriiinii dl' lliis iiiiiscK', willi llic iillier l'lal vrrliiiii il riii\s 

 ill tlie ciiiidai part iii IVoiil ol' llic M. i'ectiis. 



Again IIk' (|iiestiüii rises \vlia( the original relation of f lie nieiiibrane 

 lo llie ,M. rectus was. As in secondarj' sitnatioiis ot' tiie Miiscuii 

 oiilicj. int and transversiis tlie menihrane is found in front of the 

 i\I'. rectus, and in liio priiiiaiT condition on tlic contrary, the niem- 

 lirane, — in the cranial jiart at least — passes i)eliind the M. rectus, 

 we may suppose, that, most likely, the Membr. abdominis inter- 

 media was originally siliiated behind the M. rectus. This view is 

 strengthened by considerations of the same nature as those, which 

 we communicated regarding the M. ol»lii|. int.; only the comparatixe 

 anatomical argument cannot be applied here. 



With all examined Primates the ^^. of>!i</i//ts iwtt'nius passes in 

 front of the M. rectus. 



Tlie four elements thai compose tiie sheath of the M. rectus will 

 iiave laUen part in the forming of the sheath, as ancestral forms of the 

 now living Simiae and of man possessed, in such a way tiiat the 

 M. (ibli(|. cxt. passed in front of the M. rectus, whilst the three 

 other elements formed ilie jiosterior lamella of the sliealh. 



In the pliylogenelical developmcut. however, an iiilluence appeared, 

 which brought alioul a \ariatiou in this structure», in conseipience of 

 which the M. rectus began to show an incliualioii to pierce the three 

 elements lying behind it. This piercing begins in the caudal part. 

 The lirsl modification thai occurs, consists in the fact, that the Membr. 

 intermedia changes the relation it bears to the M. rectus and is 

 found to be situated in the caudal part in front of the M. rectus. 

 Whilst ilie pierciug-|)rocess iji ilie membrane is continuing, the M. 

 ol)ii(|. iul. in (he c;iudal jiarl begins to modify its ilirection with 

 regard to llie M. rectus. 



When llieii liie caudal part of llie M. rectus has taken its |)lace 

 between iIk» .\lnsciili obb<|. and I rausv., llie piercing-process call begin 

 to e.xteud itself also over the M. trausversus. The inoditication of 

 direction of the latter is always restricted lo the caudal part, the 

 piercing of the Membr. interm. and of the iM. oiiliq. int. by the 

 M. rectus can howexer become a com|»lcle (Uie, i. e. the piercing 

 can go so far. that in the end both (demenls are siiualeil entirely 

 ill tVoiil of the M. rectus. 



In Ihe |)liylogeiielical development which has taken place in the 

 dilli'ienl genera of Primates, the factor, that modilied the topography 

 of the Hat abdominal miLScles with regard to the M. rectus, made 

 itself felt ill varying degrees, so that the Primates that live at the 

 [ireseiit moment, tliid themselves in all sorts of phases of transformation. 



