No. 2.] VENTRAL ABDOMINAL WALLS IN MAN. 349 
not this original relation between muscle and nerve retained. 
With this view we have no grave mechanical difficulties to 
overcome in conceiving how it is possible for the simple periph- 
eral nervous system of the embryo to be evolved into that of 
the adult. It is simply that each segmental nerve grows to its 
myotome, or corresponding group of tissue or branchial arch, 
and with the further growth of muscles from myotomes the 
original nervous connections are retained. The required free 
growth of a nerve is then extremely short, as the myotomes 
receive them as soon as they leave the spinal cord, and then as 
the different muscles or parts of muscles arise from each myo- 
tome the nerve bundles split to correspond. The primitive 
muscle, then, is from its earliest appearance connected with the 
cord, and, as its muscle fibers appear and increase in number, 
this first connection guides the new nerve fibers to their 
destination. 
The studies in comparative anatomy by Gegenbaur and by 
Huxley ? all lead to the same general conclusion that nerve and 
muscle are associated with each other in their earliest stages 
of development. This idea has been the foundation for a 
number of studies in comparative anatomy, and the more it is 
investigated the stronger the foundation becomes, as may be 
seen in the critical review by Kollmann.? In a discussion of 
Testut’s “ Anomalies musculaires chez l’Homme,” Gegenbaur 4 
shows clearly that the study of variations of muscles would have 
great meaning if their nerve supply were included, and that all 
the reports of muscle anomalies for a period of more than one 
hundred years cannot be used at present, due to this omission. 
The great value of the comparative study of the muscles in con- 
nection with their nerve supply has recently been shown again 
by Ruge.® His study shows that comparison of muscles can 
be made satisfactorily only when their nerve supply is included. 
All this indicates that the history of a muscle is indicated by 
its nerve, and that in studying the development of a muscle our 
1 Gegenbaur, Grundriss d. vergleich. Anatomie. 
2 Huxley, Comparative Anatomy of Vertebrates. 
3 Kollmann, His’s Archiv, 1891, p. 76. 
* Gegenbaur, Morph. Jahré., Bd. x, p. 331. 
5 Ruge, Morph. Jahro., Bd. xix, p. 376. 
