MUSCULAR SYSTEM 89 



former state of existence. Wiedersheim l includes among the 

 atavistic muscles the m. cleido-occipitalis between the m. trape- 

 zius and sterno-cleido-mastoideus; the m. latissimo-condyloideus, 

 an appendage of the m. latissimus dorsi, very rare in man, but 

 constant in all anthropoids ; the m. epitrochleo-anconeus ; the 

 levator claviculae, and the glutaeus quartus (ischio-femoralis). 

 Klaatsch regards the short head of the m. biceps femoris as 

 atavistic in the strictest sense of the term (see Fig. 42). In 

 man the long head of this muscle proceeds from the tuber ossis 

 ischii united with the m. semi-tendinosus, but the short head 

 springs from the middle region of the posterior femoral surface, 

 directly from the linea aspera. Now, as this muscle, which is 

 possessed only by man, the anthropoids and the American pre- 

 hensile-tailed monkeys, had originally no connection with the 

 long head of the m. biceps which is supplied by the nerv. 

 tibialis, but belonged to the glutaei and was innervated by the 

 nervus peroneus, Klaatsch thinks it to be a remnant from the 

 period when the ancestors of the lower mammals more closely 

 resembled the Primates. 



According to Professor Eisler of Halle, the short head of 

 the biceps finds its homologue in the other mammals in the 

 m, tenuissimus, a muscle springing from the caudal vertebrae, or 

 from the gluteal fascia and inserted into the fascia at the distal 

 third of the tibia. This muscle is well developed in the carni- 

 vora, in certain marsupials, rodents and insectivora, as well as 

 in all the lower apes of the Old World. 



To the progressive muscles of man belong most of the 

 facial muscles of mimicry, such as the m. frontalis, and especially 

 those surrounding the eye, and the orifices of the mouth and 

 nose, as well as those placed below the cheekbone, namely, the 

 corrugator supercilii, orbicularis palpebrarum, pyramidalis 

 nasi, levator labii superioris alaeque nasi, levator labii pro- 

 prius, zygomaticus, triangularis oris quadratus menti and 

 risorius (see Fig. 43). 



These muscles are undergoing progressive metamorphosis 

 corresponding to the development of man's cranium, intelli- 

 gence and powers of speech, though they vary considerably in 

 arrangement, number, and function. 



1 Wiedersheim, loc. cit., p. 126. 



