PROGRESS OF MICROSCOPICAL SCIENCE. 
199 
the glands, but that the filaments are composed of an essentially con- 
tractile substance. 
The contraction of the filaments is produced by the following 
causes : 
Dilute acids (from 1 to } per cent.) — Sulphuric, hydrochloric, 
acetic, citric, and osmic acids. 
Dilute alkaline solutions (£ to J per cent.) — Carbonates of ammonia, 
sodium, potassium. 
Solutions of gold-chloride \ per cent., silver nitrate \ per cent., 
sulphate of quinine T \j per cent., citrate of strychnia (about) £ per 
cent., camphor ^ per cent., the poison of the cobra (about) j per 
cent., iodine \ per cent. 
Glycerine. 
Methylated spirits. 
Vapour of chloroform. 
Heat. — The temperature at which the filaments contract are rather 
variable, but are all below 57° C. 
Electricity. — The induced current causes contraction. 
Mechanical stimulation. — The filaments contract when pressure is 
made on the cover-glass. 
The evidence derived from the experiments, of which the results are 
here briefly summarized, appears to be strongly in favour of the view 
that the filaments contain true living protoplasm, and that the sudden 
movement above described is a true act of contraction ; for it the 
latter hypothesis is rejected, the only remaining view is that the 
filaments are so constituted as to be capable of undergoing coagulation, 
by which contractility is mechanically simulated. But it seems 
inconceivable that reagents of widely different natures, such as dilute 
solutions of acetic acid, of camphor, and of gold-chloride, should 
produce identical chemical effects. Osmic acid is well known to kill 
protoplasmic structures without making them contract. This charac- 
teristic reaction holds good with the filaments of the teasel when treated 
with sufficiently powerful solutions of osmic acid (e. g. 1 per cent.). 
When killed in an extended position, they cannot be made to contract 
with strong acetic acid. This observation is of importance in another 
way ; for it proves that the violent movements caused by dilute acetic 
acid are of a “ vital,” and not simply of a chemical nature. Moreover, 
the general character of the reagents and other causes (such as heat, 
&c.) by which contraction is produced is quite consistent with the 
belief that the filaments are protoplasmic in nature. 
An important series of phenomena are produced by the following 
fluids : dilute solutions (£ or £ per cent.) of carbonates of ammonia, 
potassium, and sodium, aud infusion of raw meat. If a filament under 
the mici’oscope is treated with a drop of j per cent, solution of 
carbonate of ammonia, the following changes occur. The filament 
contracts, but almost instantly recovers itself, and is once more 
protruded. The filament, however, does not regain its original 
form or general appearance : instead of consisting of thin elongated 
ropes of a highly refracting substance, it is converted into balloon- 
like or sausage-shaped masses of very transparent, lowly refracting 
