146 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the spectra observed by looking through them at the bright line were 
measured on the scale. 
Grating I. gave 5 spectra on both sides at intervals of one scale 
division. 
II. gave 8 spectra on both sides at intervals of one scale division. 
III. 10 spectra visible, interval 1 scale division. 
IV. 3 spectra, 2 scale divisions. 
V. 7 spectra, 4/5 scale division. 
VI. 4 spectra, 1 scale division. 
VII. 4 spectra, 2 scale divisions. 
VIII. 7 spectra, 3/5 scale division. 
Grating on glass in 0 • 1 mm., 6 spectra, 3 • 5 scale divisions. 
Thus, so far as the interval between the spectra is concerned, gratings 
II. and III. behave in precisely the same way as I. A difference between 
them, however, was noticed in the case of a fainter photographic proof 
in which the dark bands were not quite black : for grating I. the spectra 
2 and 4 were seen to be considerably reduced in intensity, whereas for 
gratings II.— IV. no such effect was observed. 
A muscle of Hydroplrilus observed under the Microscope by use of a 
higher objective (Zeiss JD) showed a similar reduction in the intensity 
of spectra 2 and 4. 
The result of these experiments is to show that no definite con- 
clusion as to their grating arrangement can be drawn from the diffrac- 
tion phenomena obtained from the complicated striated muscle-fibre 
of insects. No consequences, therefore, as regards their resolution in 
the direction of the Abbe diffraction theory can be drawn from the 
observation of their diffraction effects. 
The author has repeated Ranvier’s experiments on the diffraction 
phenomena of living frog’s muscle in different conditions of expansion 
and contraction, by using the Abbe method of observation. 
Fig. 24 represents the object-holder which served for the prepara- 
tion of the fresh sartorius or hyoglossus of Rana esculenta. In the 
Fig. 24. 
middle of a plate of vulcanite 0 is a rectangular opening, above which is 
cemented a glass plate G with rounded edges. On oach side of this are 
two binding-screws for the wires of an induction coil Through a hole in 
each of these binding screws passes a steel rod which carries at one end 
a small hook H and at the other a spring clip of platinum P. These rods 
are held firm by the screw S', but can be taken out and reversed if neces- 
sary. Over a small pulley at one end of the holder a thread attached to 
a scale-pan can be passed. This thread, after removal of the right steel 
rod, is fastened to the hook on the left and runs exactly above the plane 
