THE DETECTION OF ADULTERATION IN FOOD. 35 
having a sunken appearance and a bright blood-red colour. This 
inner membrane, in fact, adheres so closely to the shell as to almost 
universally follow its fracture, and so is seldom seen projecting 
from the broken edge of the husk as the outer membrane often is 
(fig. 2, ¢.), but on taking a seed that has been soaked for a day or 
so in water, or for a short time in dilute nitric acid, and squeezing 
out the cotyledon, the outer and inner membranes will be found 
swelled and softened, and can be scraped off with needles and 
examined separately. The inner one then appears as in fig. 12, d, 
and the outer one, much more swollen, as in fig. 12, ¢. 
The structure of the substance of the seed-shell is very peculiar 
and complex, and more space than is at command would be 
required to describe it fully. Its appearance, so far as identifica- 
tion is concerned, is, however, distinctive and easily recognised. 
When untreated, the shell presents in water, turpentine, or glycerine, 
the appearance shown in fig. 2, d@, when viewed with the inner 
surface uppermost: the ridges of the outer surface (4) are indis- 
tinctly seen through the shell, which appears to be composed of 
rudely hexagonal blocks containing, each, several of the small 
holes (a) with the large-celled, mottled or dinted outer membrane 
(¢) projecting in places. The appearance of hexagonal blocks is 
caused by the cell-walls of the inner membrane, for when this 
is scraped off, no such appearance is seen (fig. 2, a). By soaking 
the shell in potash or acid it is made apparent that each hole is in 
a separate block, for these are clearly seen, fig. 12, a, and can be 
picked apart with needles, fig. 12, £ The seed-shell has, however, 
a lining membrane to these blocks, for in a piece treated in acid 
and picked apart with needles, not only the outer membrane, 
fig. 12, c, the inner membrane, fig, 12, d, and the separate blocks 
(f/) of the shell are seen, but also a smaller-celled membrane, 
whose meshes correspond in size and shape to the blocks of the 
shell substance, fig. 12, ¢ In fig. 13 are shown the different 
appearances of the seed-shell under various treatments, and also in 
section. 
In the preparation of ground mustard, repeated sifting is resorted 
to to remove the fragments of the seed-shell, called “husks,” but 
minute fragments will be found in all samples if they contain 
mustard at all. 
The cotyledon of the mustard seed is composed of elongated 
cells arranged in pretty regular rows lengthwise of the seed (fig. 4). 
In most parts these rows are very regular and the cells of even size 
(fig. 5). The cells of the radicle are long and slender (fig. 6, 0). 
By chopping up with a knife the cotyledon of a soaked seed and 
crushing down the fragments in water, the separated cells will be 
seen (fig. 6). As seen in the mustard flour, the fragments of 
ground mustard will present small irregular lumps of cells, of 
