CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE, 807 
Upon the Cause of the Striation of VoLuntary Muscunar 
Tissuz. By Joun Berry Haycorart, M.B., B.Sc., F.R.S.E., 
Senior Physiological Demonstrator in the University of 
Edinburgh. [Communicated to the Royal Society, of London, 
December Ist, 1880.] 
Tue structure of striated muscular tissue has occupied the 
attention of many histologists, and various, often antagonistic, 
have been the views held from time to time since Schwann first 
investigated this difficult subject. 
I bring forward with much caution and hesitation any 
opinions of my own, nor should I venture thus far, did I 
not consider my views susceptible of direct proof, or disproof, 
not being matters of mere speculation, which may or may not 
be true, and which would tend, by their introduction to the 
literature of the subject, to make confusion worse confounded. 
In this paper an attempt will be made to account for many of 
the observed structural phenomena of muscle on simple laws of 
geometrical optics, which will, if it be successful, reduce the 
subject to comparative simplicity. I shall commence by giving 
a sketch of the views of those physiologists who have especially 
written upon the structure of muscle. This must not be looked 
upon as a complete history, for I shall leave out entirely points 
which do not concern us here. 
A short historical sketch of the views held upon the structure 
of striated muscle.—The writings of Mr. Bowman form the most 
important and brilliant contributions to the literature of this 
subject, and taking him as a landmark, it is convenient to speak 
of investigators before or after his time. Among the former 
Schwann, quoted; by Miiller (‘ Physiology,’ translation by 
Baly, vol. ii, p. 878), describes the striated voluntary fibre, in- 
dicating its shape and size. The cross markings were observed 
by him, and, indeed, with one or two remarkable exceptions, by 
all the early observers (Lauth and Wagner, in Miiller’s ‘ Archiv 
fir Anatomie und Physiologie, und Wissenschaftliche Medicin,’ 
pp. 4 and 318 of the year 1835). Schwann, with Bauer, 
Krause, Miiller, Home, Valentin, and Milne Edwards recognised 
the important fact that each fibre is composed of a number of 
threads or fibrillz, packed side by side and joined together by a 
transparent tenacious fluid (Krause), and, moreover, that these 
threads or fibrille are cross striated, as is the fibre itself. 
Although Schultze describes the fibrille as being uniform fila- 
ments, he is alone in this opinion, most of his contemporaries 
