564 
POISONOUS METALS IN CHEESE. 
to its mysterious form and wonderful properties, let us pause 
to reflect for a moment on the minuteness of their organs, by 
which the smallest fern and the largest tree in the forest is 
fed and sustained. Microscopic mouths in the leaf suck in 
gaseous food from the air ; the extremities of microscopic 
hairs suck a liquid food from the soil. 
We are accustomed to admire, with natural and just as- 
tomshment, how huge rocky reefs, hundreds of miles in 
length, can be built up by the conjoined labours of myriads 
of minute insects labouring together on the surface of a coral 
rock; but it is not less wonderful that, by the ceaseless 
working of similar microscopic agencies in leaf and root, 
the substance of vast forests should be built up and made 
to grow 7 before our eyes. It is more wonderful, in fact; for, 
where in the one case “ dead matter” extracted from the sea 
is transformed onlv into dead rock, in the other the lifeless 
matter of the earth and air is converted by these minute 
“ plant-builders ” into living forms, lifting their heads aloft 
to the sky, waving with every wind that blow r s, and beauti¬ 
fying whole continents with the varying verdure of ever- 
changing leaves. 
POISONOUS METALS IN CHEESE. 
At the late meeting of the British Association for the 
Advancement of Science, Professor Voelcker stated that 
he had detected both copper and zinc in cheese; in some 
specimens copper, in others zinc, and in some both copper 
and zinc. The descriptions of cheese in which these poi¬ 
sonous metals were found were double Gloucester and 
Stilton. Skimmed-milk cheese, which was likewise examined 
for copper and zinc, did not contain any metallic impurity. 
Inquiry led to the discovery that in many dairies sulphate of 
copper, and sometimes sulphate of zinc, are employed in the 
making of cheese. The reasons for which these prejudicial 
salts are added to the cheese are variously stated. Some 
persons added sulphate of zinc, with a view of giving new r 
cheese the taste of old! Others employed sulphate of 
copper for the purpose of preventing the heaving of cheese. 
Dr. Voelcker also stated that he had found alum in Gloucester 
cheese, and mentioned that he had learnt that in some dairies 
alum was employed to effect a more complete separation of 
the caseine from the whey. In the course of his experiments 
the Doctor said he had found that copper and zinc cannot 
be detected in an ash when much carbon is present. 
