1881.] The Border -land of Chemistry and Biology, 321 
kilo, in the first, 0*007 in the second, and 0*004 for iron, all 
in the form of sulphates. 
Here we are, in the first place, struck with the difference 
between iron in its two classes of salts, the ferrous and the 
ferric. Of the former the fatal quantity is 0*115 grm. per 
kilo., or twenty-eight times as much of the latter. 
We next perceive that the distinction between poisonous 
and non-poisonous substances is reduced to a mere question 
of proportion. The dogma that “ whatsoever is poisonous 
in large doses is poisonous also in the smallest, though the 
injury done may escape notice,” falls at once to the ground 
if we reflect that the very salts which naturally occur in and 
form necessary parts of our blood become deadly in a some- 
what larger quantity ! 
Among the non-metallic bodies the compounds of chlorine, 
bromine, and iodine were found accordant in their physiolo- 
gical reactions, but the increase of intensity accompanying 
the atomic weight was not observed — a most puzzling ex- 
ception. The identity of aCtion here noted is also peculiar, 
since bromides taken internally have a very different aCtion 
from the corresponding chlorides, e.g., in the treatment of 
sea-sickness. Phosphorus, arsenic, and antimony occasion 
no immediately perceptible physiological reaction, though if 
arsenious acid is injected in the proportion of 0*56 grm. per 
kilo, it arrests the pulmonary circulation. Sulphur and se- 
lenium agree in their physiological aCtion ; the latter, having 
the higher atomic weight, is the more powerful. 
A curious exception to the rule that isomorphous sub- 
stances agree in their physiological aCtion is afforded by the 
salts of potassium and ammonium. The effects of the latter 
approach those of certain nitrogenous alkaloids. 
The author suggests that if — as is far from impossible — 
the carbon-compounds present similar phenomena in their 
influence upon animal life, a new key to the molecular rela- 
tions of organic bodies is placed in the hands of the chemist. 
It is especially to be remembered that in alcohols of one and 
the same series the intensity of the physiological aCtion rises 
with the atomic weight, as has been shown by Dujardin. 
The question in what manner the isomorphous relations and 
the atomic weights of substances can influence their physio- 
logical aCtion can scarcely as yet be entertained. 
Still Dr. Blake’s researches are exceedingly valuable, both 
as pointing out a new method of chemical research and as 
overturning certain erroneous conceptions concerning the 
nature of poisons. 
