Charles Eussell Bardeen and Warreu Harmon Lewis 



25 



neural and transverse processes of the vertebrae is shown in the cervical 

 region in Fig. D. The extent of development of the ribs is shown in 

 Fis. E. 



Fi^. 24. Diagrammatic cross section through the 6th-7th thoracic segments of 

 Embryo CVI. x 35 d. This figure is made to correspond with Figs. 31 and 23. See 

 legend for Fig. 31. 



The musculature has undergone most marked changes. The dorsal 

 musculature is slightly separated from the ventro-lateral by vascular 

 mesenchyme. The dorsal musculature is further subdivided into three 

 muscle columns. These correspond to the ileo-costal, longissimus dorsi 

 and spinalis groups of dorsal muscles in the adult. The ventral muscula- 

 ture is likewise subdivided into two main portions, the rectus muscle 

 and the lateral musculature. The last is further subdivided into ex- 

 ternal oblique, the intercostals, the internal oblique, and the transversalis 

 muscles. In the intercostal muscles alone is the segmentation charac- 

 teristic of the mvotomes fullv maintained. 



