Draper & Moss — O^i some Forms of Selenium. 529 
that part of the tendon of flexor digitorum longus which goes to the third 
digit, the other portion from the inner aspect of the same bone is inserted 
along with the tendons to the other two digits. Professor Humphry de- 
scribes accessorius as being single, large, taking origin from the anterior 
and outer surface of the calcaneum, and inserted into the three digit 
tendons. 
In the ankle joint the motion is one of extension and rotation 
inwards, and flexion and rotation outwards ; the anterior ligament 
is weak and membranous, the internal lateral is very strong, going 
downwards and backwards to the astragalus and calcaneum, the ex- 
ternal lateral is broad. The astragalus is capable of lateral rotation 
on the calcaneum, has an anterior metatarso-astragular, and a poste- 
rior calcaneo-astragular, but no lateral, stays. 
The muscles of the digits are, abductor and adductor indicis and 
medii, all more or less fused ; abductor annularis from the rudimentary 
fifth metatarsal to the extensor tendon of the outer digit ; adductor 
annularis from the fourth metatarsal to the same digit. The two 
plantar interossei send in two slips on the plantar aspect of the 
foot. , 
XLYII. — On some Forms of Selenium, and on the Influence of Light 
ON THE Electrical CoNDUcnviTr of this Element. By Harry 
Draper, F. C. S., and Eichard J. Moss, F. C. S. 
[Bead November, 10, 1873.] 
In a paper read before the Society of Telegraph Engineers* on February 
12th, 1873, Mr. Willoughby Smith announced the remarkable fact, 
that a bar of crystalline selenium, through which a current of electri- 
city passes, has its conductivity increased 15 to 100 per cent, when the 
bar is exposed to light. The light from an ordinary gas burner placed 
at a distance of several feet increased the conductivity 15 to 20 per 
cent. Mr. Smith satisfied himself that alterations in temperature in 
no way afl'ected this result, by placing the selenium in water, in sach 
a manner that the light from burning magnesium ribbon held some 
inches above the bar passed through about an inch of water before 
falling upon the selenium. Under these circumstances, the conduc- 
tivity of the bar was found to increase more than two-thirds, returning 
to the normal conductivity when the light was withdrawn. 
Lieutenant Sale, in a communication made to the Royal Society, | 
describes a series of experiments undertaken with the object of ascer- 
* Nature, vol. vii., p! 203. 
t Proceedings of the Royal Society of London, volume xxi. p. 283. 
