THE DEVELOPMENT OF THE MUSCULAR SYSTEM. 315 



The development of the individual muscles from the myotomes, including the migration 

 of the myotomes and the fusion and splitting of the myotomes or muscles, is an extremely 

 difficult subject for practical study. Certain points can be made out from individual sections, 

 but a complete study is possible only from serial sections of embryos in many stages of 

 development. Even with serial sections it is usually necessary to make wax reconstructions 

 of the muscles in different stages of development in order to show their relations to one 

 another and to the surrounding structures. For methods of reconstruction see Appendix. 



For gross study, embryos (human or animal) fixed and stained by any ordinary method 

 will serve. Possibly the best results are obtained by fixing the embryos (pig embryos are 

 usually easily procured) in Zenker's 'fluid, cutting serial transverse sections in paraffin, 

 and staining with Weigert's haematoxylin and eosin. In sections treated* by this method 

 the developing muscle fibers are usually stained a more brilliant red than the surrounding 

 structures. 



For histogenesis of muscle tissue, striated voluntary or heart muscle, the following 

 technic yields good results. Fix small pieces of the developing muscle tissue (whole 

 embryos if not more than 10-12 mm. long) in Carnoy's acetic-alcohol mixture. Cut thin 

 sections in paraffin, and stain with Heidenhain's hasmatoxylin (see Appendix. A counter- 

 stain with eosin adds to the differentiation. The haematoxylin brings out the anlagen of the 

 fibrillae. 



Reference for Further Study. 



Bardeen, C. R.: The Development of the Musculature of the Body Wall in the Pig, 

 Including its Histogenesis and its Relation to the Myotomes and to the Skeleton and to the 

 Nervous Apparatus. Johns Hopkins Hospital Reports, Vol. XI. 



Bardeen, C. R., and Lewis, W. H.: Development of the Limbs, Body Wall and Back 

 in Man. American Jour, of Anat., Vol. I, 1901. 



Bolk, L.: Die Segmentaldifferenzierung des menschlichen Rumpfes und seiner Extremi- 

 taten. Morph. Jahrbuch, Bd. XXV, 1898. 



Futamura, R.. Ueber die Entwickelung der Facialismuskulatur des Menschen. 

 Anat. Hejte, XXX, 1906. 



Godlewski, E.: Die Entwickelung des Skelet- und Herzmuskelgewebes der Saugetiere. 

 Arch. }. mik. Anat., Bd. LX, 1902. 



Grafenberg, E.: Die Entwickelung der menschlichen Beckenmuskulatur. Anat. 

 Hejte, 1904. 



Heidenhain, M.: Structur der contractilen Materie. Ergebnisse der Anat. u. Entwick., 

 Bd. VIII, 1898. 



Heidenhain, M.: Ueber die Structur des menschlichen Herzmuskels. Anal. Anz., 

 Bd. XX, 1901. 



Kastner, S.: Ueber die Bildung von animalen Muskelfasern aus dem Urwirbel. 

 Arch. f. Anat. u. Physiol., Anat. Abth., Suppl., 1800. 



Keibel, F., and Mall, F. P.: Manual of Human Embryology, Vol. I, 1910. 



Kollmann, J.: Die Rumpfsegmente menschlicher Embryonen von 13-35 Urwirbeln. 

 Arch. f. Anat. u. Physiol., Anat. Abth., 1891. 



Lewis, W. H.: The Development of the Arm in Man. American Jour, of Anat., Vol. I, 

 1902. 



Matjrer, F.: Die Entwickelung des Muskelsystems und der elektrischen Organe. Also 

 Bibliography. In Hertwig's Handbuch der vergl. u. experiment. Entwickelungslehre der 

 Wirbeltiere, Bd. Ill, Teil I, 1904. 



