28 



PldlijrrJiuii (iMycetes iii^er, Cliry.sutlii'ix sciiirca iuid Iliipalfj. 



lu iig'. 4 are re|ireseiite(l sections tlu-ongli (lie slieatli ol'tlie M. rectus 

 ot' Mdii. Tlie Al. ol)li(|. ext. passes entirely iii tVoiit of tiie M. rectus, 

 the Meiiilir. iiitenii. fails. Crauiallj from tlio linea Dougiasii llie 

 M. obliq. int. possesses two layers, and the AI. Iransv, extends behind 

 tlie M. rectus (fig. 4a), caudallj from the linea semicircularis tlie 

 aponeuroses of the three Hat muscles of the abdomen are situated 

 on the anterior surface of the M. rectus (fig. 4/> and 4r-). 



The 5''' figure relates to llie sheath of a Cercopithecu-s cynt>sHra.i. 

 As appears from the sections, the M. obliq. ext. and the membr. 

 intcrm. pass entirelv in front of the M. rectus, the M. obli([. int. 

 which runs also before the AI. rectus, possesses moreover in its 

 most cranial part for a short distance a layer which passes behind 

 the Al. rectus (tig. öa); soon however this layer ceases (fig. bh). 

 The AI. transversus, which in the cranial part extends behind the 

 Al. rectus, sends in the caudal third part ils aponeurosis likewise 

 before the Al. rectus (fig. 5c and 5(/). 



Figure 6 relates to the vagina AI. recti of Si'innnp'itliern.s cnti'llu.s. 

 The M. obliq. ext., the Alembr. iiiterm. and the AI. oblitp int. pass 

 entirely in front of the Al. rectus. The Al. transv. however runs in 

 the cranial '/, j)art of the sheath behind the AI. rectus (fig. (ia), in 

 the caudal 4''' ^)art its a|)oneurosis takes part in the forming of the 

 anterior lamella of the sheath (fig. 6/j and tjr). A condition of the 

 vagina Al. recti as represented in fig. (5, can be admitted as normal 

 for Katarrhini ; 1 found it with Cercopithecus jiatas, Alacacus cyno- 

 molgus, Colobus gueresa. Semnopithecus entellus, Cynocephalns 

 hamadryas, Siamanga syndactylus, Orang utan. 



From this short description it appears that monkeys show great 

 differences with regard to the composition of their rectal siieath, 

 differences of such importance, that it seems in the beginning 

 difilicult to see a connection between all the conditions that present 

 themselves. It will consequently be our task to try and find such a 

 connection founded on the evidences given above. With this purpose 

 we shall trace of each of the four elements that take part in the 

 forming of the sheath separately how the relation is it bears to 

 the M. rectus with the different Primates. 



With Flatyrrliini the M. tramTersus passes entirely into the j)OSt- 

 erior wall of the sheath, with Katarrhini and with man this con- 

 dition exists only in the cranial part; in the caudal third or fourth 

 parts the AI. Iiansv. lakes part in the foi'miiig (if the anterior wall 

 of (he slicalli; Willi a .Macaciis rhesus I dissected, the aiioneiirosis 



