FACTS AND OBSERVATIONS. 
467 
Antidote for Arsenic. — A writer in the Chemical 
News suggests that, to obtain the peroxide of iron in a 
hydrated state, a solution of the persulphate of iron should 
be kept, and ^Yhen the oxide is wanted to add to it calcined 
magnesia in excess. This mixture being administered, saves 
the trouble of washing the precipitate, and at the same time 
gives a purgative to the patient. 
The Blood-corpuscle. —Dr. Roberts, at a meeting of 
the Microscopical Section of the Manchester Literary and 
Philosophical Society, exhibited some mounted specimens 
of blood-corpuscles from albuminous urine, which showed 
an appearance as if the contents of the cells had separated 
from the cell-wall, and become aggregated round the centre, 
like a nucleus. When these corpuscles were treated with 
magenta, the central portion was either not coloured at all 
or only faintly so, whereas the circumferential portions be¬ 
came deeply tinted. By treating fresh blood with an excess 
of a solution of carbolic-acid this appearance could be pro¬ 
duced at will. In the blood-corpuscles of the fowl a similar 
effect was produced by the carbolic-acid solution; the cell- 
contents appeared to detach themselves from the cell-wall 
and to collect round the nucleus. The appearances pre¬ 
sented strongly suggested the idea that the cell-envelope of 
the blood-disc was a double membrane; that the inner sepa¬ 
rated under certain circumstances from the outer membrane, 
and shrank in toward the centre. Dr. Hensen, of Kiel, 
seems to have convinced himself that such is the case in the 
blood-disc of the frog, and he compares the inner membrane 
to the primordial utricle of the vegetable cell. Of the pro¬ 
longations described by Dr. Hensen, as stretching radially 
between the shrunk inner membrane and the outer one, Dr. 
Roberts saw nothing. If the said view of the structure of 
the blood-cells were substantiated, it would greatlv facilitate 
the explanation of the effects produced on these cells by 
magenta and tannin. 
Black Skin and Periosteum.— We noticed the occur¬ 
rence of this in fowls in a previous number. Mr. W. B. 
Tegetmeir, writing on Variations in Plumage,^^ in the 
Intellectual Observer, states that under the title of Coq a 
Duvet,^^ Temminek has described those birds which are 
known at our poultry shows under the title of sllh fowls. 
Of these birds he adds, I possess several specimens. They 
are brought from many parts of eastern Asia and the Indian 
Archipelago. They are small in size, and are remarkable as 
