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VII. On the Development of Striated Muscular Fibre. By Wilson Fox, M.B. Lond., 

 Professor of Pathological Anatomy at University College, London. Communicated 

 by Dr. Sharpey, Sec. U.S. 



Eeceived June 15, — Eead June 15, 1865. 



A CORRECT knowledge of the structure of the animal tissues has long been recognized as 

 an almost essential preliminary to a full comprehension both of their physiological 

 functions and also of the phenomena presented by disease, and the aid afforded in an 

 inquiry into adult structure by the study of the processes of embryological formation has 

 been fully appreciated. 



While, however, the mode of growth of most of the tissues in question has been 

 more or less completely elucidated, the development of striated muscular fibre has still 

 remained a subject of considerable uncertainty, regarding which the most varied and 

 even opposing views have been brought forward by observers who have made it an 

 object of research. Feeling desirous, on pathological grounds, of attaining to some 

 fixity in my own opinions on this question, I have during some months made it a subject 

 of renewed study, and with results, which may, I venture to hope, assist at least to an 

 elucidation of some of the points in dispute. 



My observations have been conducted upon the Tadpole, Chick, Sheep, and human 

 embryos at various stages of growth ; and I hope to be able to show that the processes 

 observed are essentially identical in all these classes. 



Tadpoles (which offer by far the easiest objects for this investigation) are best exa- 

 mined immediately after they have emerged from the egg. The examination is much 

 facilitated by placing them for a few hours in an extremely dilute solution of chromic 

 acid (^ to Y^ V^^ cent.), or (what is far better) in solutions of bichromate of potash of 

 from 1 to 4 per cent. They should subsequently be immersed in Beale's carmine and 

 glycerine solution *, which renders the nuclei more apparent. The embryo chick is also 

 best examined after immersion for a day or two in weak solutions of bichromate of 

 potash (chromic acid is unsuitable for these preparations), and subsequent staining with 

 Beale's solution. Sheep larger than | an inch maybe examined after preparation in chromic 

 acid of from ^ to 1 per cent. ; at earlier stages either bichromate of potash or a mixture 

 of alcohol, glycerine, and water forms a good medium ; but in all instances I have found 

 Beale's carmine an excellent help in this investigation. The structure of the early stages 

 of the muscular fibre of the Tadpole may be investigated with a magnifying power of 



* How to Work with the Microscope, p. 201. 

 MDCCCLXVI. Q 



