OF MICROSCOPIC OBJECTS. 17 
Gelatin, chondrin, and osseine are the result of the boiling 
of animal membranes, skin, tendons, and bones, respectively 
at a high temperature for a sufficient time. They are 
insoluble in cold water, but easily dissolved by the use of 
heat. Alcohol, corrosive sublimate in excess, nitrate of 
mercury, and, most characteristically, tannin, precipitate 
gelatine—the latter when it is very largely diluted. 
* Skin and tendons contain a substance which resists the 
action of boiling water for many hours. It is insoluble in 
cold concentrated acetic acid, but by long-continued boiling 
in it, is gradually dissolved, and more easily in hydrochloric 
acid.” (Fownes.) 
Horny substance—keratin, found in hair, nails, feathers, 
and epithelium, is obtained by finely dividing them, treat- 
ing them with hot water, and afterwards by boiling alcohol 
and ether. The horny substance is then very soluble in 
caustic potash. 
Of bones we have already spoken. 
It has been mentioned elsewhere in this work, that all 
the internal organs of insects may easily be dissolved out by 
boiling in liquor potassz, leaving their external chitinous 
structures, limbs, &c., unaffected. But this is a proceeding 
much to be deprecated, for various reasons which it is 
scarcely necessary to give here... It is far better to treat 
them in another way, by which these organs may be ex- 
amined im situ, at least to a very great extent, as will 
presently be shown. 
The parenchyma of leaves and many other vegetable 
structures may be decomposed by prolonged maceration in 
water, and then easily be washed away. Nitric acid, vary- 
ingly diluted, will produce the same effect more speedily, the 
objects not requiring the same amount of bleaching subse- 
quently. But by far the best and most speedy method is, 
to place them in the liquid manure tank of the gardener 
for a sufficiently long maceration. The results of this plan 
are exquisitely beautiful. 
