24 



111 aocoidiince with lliis is llie fact, that the lilues of the "M. obliq. 

 ext. prof." — for this name should be applied to the muscle — 

 found by me with Siamang show a direction tliat is almost parallel 

 with that of the fibres of the M. tM\([. ext. 



Further 1 will still remark in Ihis connection, that according to 

 Tkstut ') and liK Dorm, e 'j several investigators have described by 

 different names, and especially by that of "M rectus lateralis" as 

 variations muscles of man, situated between the Musculi obliq. 

 exteriius and internus and corresponding in the direction of their 

 fibres with the M. obliq. ext. In the most typical cases Ihis "M. 

 rectus lateralis" originates from the 9''' to the 11''' rib, runs then 

 almost vertically downwards and is inserted into the crista iliaca. 

 It is obvious that we have to do here with the remaining part of 

 the M. obliq. ext. prof., occurring as atavism, which muscle normal- 

 ly has been entirely reduced in man, whilst not even a membrane 

 has remained. The variation has been described by the name of M. 

 rectus lateralis. This name, though with regard to the direction of 

 the fibres very correct, is however not preferable, as it could give 

 rise to the entirely wrong notion, that this muscle is connected in 

 some way or other with the M. rectus abdominis. In fact the two 

 have nothing to do with each other. Consequently we had better 

 call this variation M. obliq. ext. profundus, a name to which, as 

 comparative anatomy teaches us, it has an indisputable right. 



In conclusion be remarked tliat, in accordance with Eisi>kr, I 

 think it likely, that the deep origins of the M. obliq. ext. (vide 

 before) described by him, can also be considered as remaining parts 

 of the M. obliq. ext. prof. 



It still remains to trace the relation the Membr. abdominis inter- 

 media bears to the M. rectus : the membrane namely, as I commu- 

 nicated already takes part in the formation of the sheath of the M. 

 rectus. With the description of the structure of the sheath of the 

 different monkeys the relation of the membrane to the M. rectus 

 will consequently likewise be discussed. 



On the structure of the shentli of the M. rectus of Primates. 



The relations the four elements, that compose the rectal sheath, 

 bear to the M. rectus with the different monkevs will be brieflv 



') L. Testut. Les anomalies musculaiies cliez Thomme, expliquées par ranalomie 

 comparee, leur impoi'tance en antliropologie. Paris. 1804. 



2) A. F. Le Double. Traite des variations du système miisculaii- de riionime el 

 ^ leur signification au point de vue de Tanthi-opologie zoologique. Paris. 1897. 



