828 JOHN =SRRY HAYCRAFT, 
the clear stripes or valleys by lines, just as they are so joined 
across the dark stripes, although the lens must be depressed 
ever so little to make this out. These lines are, in fact, nothing 
more or less than the longitudinal strize described many years ago 
as lying between the fibrillee of which the fibre is composed, 
these little knobs lying in their course. This can, perhaps, 
most conclusively be made out in the following way :—Allow a 
piece of insect’s muscle to remain in a drop of water for some 
hours (which will vary with the temperature) until it has par- 
tially putrefied. Then cover and examine, when many of the 
fibres will have separated towards their ends into fibrille. One 
can then distinctly trace the chinks between the separated fibrillee 
as being continuous with the striz, on which the knobs are still 
seen in the centre of the fibre. I think that the following is a 
feasible explanation of these knob-like enlargements of the 
cementing substance seen as longitudinal strie. These knobs 
occur, as will be beautifully seen on referring to the woodcut in 
Quain, on the slopes between the valleys and the ridges. The 
cementing substance dips down here with the fibre itself, and if 
there be the slightest lateral obliquity it will appear larger. 
You see the cementing matter on edge, and differing as it does 
from the muscle-substance in refrangibility, a distortion occurs, 
giving rise not toa dark line as on the surface, but to a dark knob. 
This is, in fact, but an optical delusion, for the striz are quite 
uniform, and were the fibre cylindrical would appear so. This 
may be proved by the fact that very often if the rays of light 
from the reflector are oblique, but one set of dots appears, which 
shift over to the other side on twisting the mirror. By shifting 
the preparation about, or by twisting the tube of the microscope 
obliquely, the dots disappear from one part of the fibre to appear 
in another, showing that it is but an optical effect, and that no 
structure here exists. 
Before concluding I must gratefully acknowledge much help 
and sympathy which I have received in this investigation. 
To Professor Tait I have gone when in any difficulty, for an 
observer in a case such as this must have the aid of an ex- 
perienced physicist, otherwise grievous error is but courted. To 
him, as has been seen in the text, I owe many suggestions, and 
he has kindly entirely looked over my paper. Dr. Klein has 
shown me great kindness in carefully examining wy preparations 
from the histological point of view, and as has before been men- 
tioned, in showing me preparations to corroborate my views. 
My thanks are due to my friend Mr. Priestley for many useful 
hints, especially concerning the literature of the subject. 
