314. JOHN BERRY HAYCRAPFT. 
what to believe, for there is such entire disagreement among 
physiologists as to simple facts, to say nothing of any conclusions 
which may be drawn from them. Thinking that there must be 
some simple clue which would solve the whole problem, I com- 
menced to work at the subject in the summer of 1878. At the 
onset the clue was discovered, and the substance of the present 
paper was written by the end of that year, before I had read for 
the first time the paper of Mr. Bowman’s, in the ‘ Transactions’ 
of this Society. My astonishment was indeed great to find in 
it the first glimmerings of my own opinions, for although the 
subject had then been worked out but in the rough, and he had 
a much simpler problem to deal with, yet undoubtedly he held 
the same views in the main. My obvious course was, therefore, 
entirely to rewrite my paper, making every acknowledgment to his 
already published work. Mr. Bowman considered, as far as I can 
make out, that the light stripe was to be compared with the 
cement seen in longitudinal fibrillation between the fibrille, yet 
he looked upon the striz as being due to the shape of the fibre. 
From the history of the subject, which has just been given, it 
will be seen that all observers are not agreed as to the actual 
appearances of a striped fibre, and especially the changes which 
occur during contraction, and we hold that they have fallen into 
great and unwarrantable error in the conclusions (these, indeed, 
are all contradictory) drawn from these appearances. A fibre 
has been observed in the field of the microscope, which is marked 
transversely, as already described, and all modern investigators 
have concluded that the transverse bands mark the positions of 
discs (seen on edge) of tissue of different refractive indices and 
chemical composition, alternating in the long axis of the fibre. 
This is, however, purely an assumption which in no way 
follows. 
We can also account for all these cross markings in a way 
which involves no theory, and requires for its appreciation but a 
knowledge of most elementary geometrical optics. 
If a small fragment of muscle be teazed out in water, salt 
solution, or almost any other fluid, and examined in the ordinary 
way with a power of 300 diameters or more, the important fact 
may be made out which is the basis of all these future observa- 
tions, that the borders of the fibres are not smooth, but undulate, 
presenting wavy margins (Fig. 1). 
In the fresh unstained preparation there is a halo around the 
edge of the fibre which masks this appearance, yet by carefully 
adjusting the mirror so as to obtain oblique light, or by search- 
ing fora fibre partly in the shade of another, the crenulated border 
may be made out ; in the case of insects’ muscle this is, however, 
always easy to demonstrate, for the fibres are much coarser, in- 
