1885.] 
Silk and its Secretors. 
345 
VIII. SILK AND ITS SECRETORS. 
E pee a spider spinning its net or a caterpillar lower- 
ing itself by a thread from the branch of a tree. 
But little do we think how many unsolved questions 
hang suspended on the silken lines. True, we know some- 
thing about silk ; our microscopists teach us that the thread 
of the silk-worm consists of two solid poreless rods like 
metallic wires laid side by side and cemented together; 
whilst the spider’s line is composed of many such parallel 
strands, in some cases over a thousand, though each far 
more minute than the single line of a caterpillar. Our 
chemists have analysed this strange secretion and find that 
it consists of an outer, less compact portion, known in the 
trade as “ gum,” whilst within lies the true silk, named 
fibrioneor sericine. Both these parts are composed of oxygen, 
hydrogen, carbon, and nitrogen, but the gum is less compact 
than the sericine, and can consequently be removed by a 
careful application of soap and water. 
Last, though assuredly not least, our rogues have made 
the question of “weighting” or “loading” silk a matter 
of anxious study and of year-long experimentation, and are 
now prepared to convert one pound of silk into four or five 
pounds of something devoid of all the properties which 
render silk valuable, but which at any rate can be sold as 
silk. 
But all this knowledge takes us but a very little way. 
Silk, it seems, is a compound of the so-called four organic 
elements. Its thread has therefore been likened to a thread 
which we might draw out of a solution of gelatine. But 
there are some capital differences. All the other nitrogen- 
ous portions of the organic system, liquid or solid, if exposed 
to the air in thin layers, pass very readily into putrefaction 
and decomposition. Not so silk. We may chop up rags 
or threads of silk and strew them on the fields or dig them 
into the soil. They may be exposed to heat and to frost, to 
sunshine and showers, to dew and wind. But in no reason- 
able time will they decay and return to the earth. Thence, 
unlike shoddy, hair, horn-shavings, all very similar to it in 
composition, save in one point only, silk, however plentiful, 
is of no value as plant-food. If a farmer were offered five 
tons of pure silk at ten shillings per ton he would be foolish 
if he accepted the offer and spread it on his fields. 
VOL. VII. (THIRD SERIES) 2 B 
