92 /Medical Chemistry. 
in various stages; that in some instances he has seen it in 
common with all other remedies, completely fail, and the 
unhappy patients pursue their downward progress to the 
grave: that on the contrary, in a great number of instances, 
he has seen a sensible amelioration in the most distressing 
symptoms ; the cough has become less frequent ; the ex- 
pectoration more free, and the sleep more prolonged. 
“It is (adds Dr. Magendie,) with satisfaction easily un- — 
derstood, that | have seen the symptoms of phthisis com- 
pletely cease in eight (seven ?) different circumstances ; in 
three children from four to six years, in a young woman of 
fifteen, in another of twenty, in a young man of twenty five, 
and in an old man of sixty-six ; and it is with the most anx- 
ious solicitude, that I have waited their state of health, for 
the purpose of learning, whether the evil is really arrested, 
or only suspended in its progress. 'Time only can decide; 
I can only say that the two ladies whose cases were reported 
in my first memoir, and whose cure is of four years stand- 
ing, continue to enjoy perfect health.” 
With respect to the dose, Dr. Magendie remarks, that as 
the effect of the prussic acid is very different in different in- 
dividuals, it is necessary to begin with a moderate dose; 
but there is no danger in encreasing it provided its effects 
are not manifested, and that he has, many times, gradually 
augmented the dose to half a drachm in twenty-four hours 
without producing the slightest inconvenience. 
As to the preparation of the acid, Dr. Magendie finding 
that the acid of Scheele is of variable strength, prefers that 
prepared by the process of Gay Lussac, which consists in 
decomposing the prussiate of mercury by muriatic acid and 
collecting the acid in a cold receiver. This acid is to be 
diluted with six times its volume or eight and a half times 
its weight of distilled water. 
Remark. As the preparation of the acid of Gay Lussae 
is not without danger to the operator, on account of its ter- 
rifie energy, even in vapour, it is presumed that having once 
ascertained how much of Gay Lussae’s acid, a given weight 
of Prussiate of Mercury will afford, it will be sufficient te 
place at once in the receiver, eight and a half parts. of water 
and thus obtaim a diluted and much less dangerous acid. 
I have found very unpleasant effects even from breathing 
the vapour of the prussic acid when I have prepared it after 
