GLANDULAR HAIRS OF THE COMMON TEASEL. 171 



Methylated spirits. 



Vapour of chloroform. 



Heat. — The temperatures 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, whose results 

 are here briefly summarised, appears to be strongly in favour 

 of the view that the filaments contain living protoplasm, and 

 that the sudden movement above described is a true act of 

 contraction. For if the latter hypothesis is rejected, the only 

 remaining view appears to be that the filaments are so con- 

 stituted as to be capable of undergoing coagulation, by which 

 contractility is mechanically stimulated. But it seems in- 

 conceivable 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 contact. This characteristic 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 im- 

 portance in another way ; for it proves that the violent move- 

 ments caused by dilute acetic acids are of a " vital," and 

 not of a simple 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 car- 

 bonates of ammonia, potassium, and sodium, and infusion of 

 raw meat. If a filament under observation is treated with 

 a drop of -\ 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 threads 

 of a highly refracting substance, it is converted into balloon- 

 like or sausage-shaped masses of very transparent, lowly 

 refracting matter. These transparent masses are remarkable 

 for the spontaneous changes of form and other quasi-amoeboid 

 movements which occur among them. 



Dilute infusions of meat cause a similar effect, astonishing 

 quantities of transparent matter being produced. 



VOL. XVII. NEW SER. M 



