822 JOHN BERRY HAYCRAFT, 
For this experiment the fresh fibres of insects’ muscle should be 
examined, for, with fine mammalian muscle, the light is not so 
good, owing to the higher power required. This experiment 
has been introduced here with the description of stained muscle, 
not that it can be strictly compared with an ordinary staining 
process, but simply to show what an influence the fibre’s shape 
must have upon the tinting, supposing, as we do, that this is in 
reality uniform. 
An investigation such as this is beset with many difficulties 
and fallacies, and I may mention one which befel me in this 
stage of my work. 
I had stained a few muscular fibres of a rabbit with picro- 
carmine, and on examination, what was my surprise to find that 
in some of them the light stripes (valleys) were most brilliantly 
stained with carmine. I was long puzzled at this, when it was 
last discovered that the picro-carmine had dried somewhat on 
the preparation, and the carmine had mechanically precipitated 
along the valleys, filling them up. At the end of one or two 
fibres this precipitation had partially peeled off, showing 
undoubtedly the true nature of the phenomenon. 
_ I have in my possession very beautiful alcoholic preparations 
stained with logwood. At first sight, from a study of many of 
the fibres, one would be led to beueve that the bright stripe is 
wholly unstained, while the dark stripes are of a beautiful violet. 
A careful examination, however, reveals the fact that such 
fibres are broken up transversely, looking like piles of coins, a 
very common occurrence, especially in preparations that have 
been long mounted. The coins, lying close to one another, 
with narrow chinks between, of course revealed transverse 
unstained tracts, which could well be mistaken for the bright 
stripe. 
Mae interest and discussion has hitherto accrued to the 
action of muscle on polarised light than to the effects of stain- 
ing reagents. We have seen that much difference of opinion 
exists; Briicke has maintained that not only is the dark stripe 
(ridge), as all are agreed, doubly refracting, but that the whole 
of the light stripe is isotropous. I myself was led to modify 
this, discovering that on careful focussing with a fibre not at all 
sheared in its length, the central part of the light stripe was 
undoubtedly anisotropous. ‘This I have afterwards seen figared, 
as before mentioned, in Hermann’s ‘ Physiology,’ and have 
introduced the diagram into Fig. 2. It is a point of some 
practical difficulty to mark exactly the positions of the cross 
bands while turning the analyser, and thus changing the char- 
acter of the field. ‘This difficulty has been overcome completely 
by a suggestion of Professor Tait’s, who has helped me much in 
