FILAMENTS OF THE CYNARE. 191 
it was irritated was -°+." broad, became after irritation 
Ty 
12"; another, from a width of 2%," acquired one of 
160 27 
9". and a third, from +!;!5,'" became 12.5 
In close connection with this is the circumstance that the 
cells before shortening are longitudinally, and after it trans- 
versely, striated. 
In his former memoir, Professor Cohn had come to the con- 
clusion that, in their elongated condition, the cells of the fila- 
ments were ina state of active extension, and that the shorten- 
ing, either upon irritation or after death, depends upon a 
relaxation, in consequence of which the elasticity which had 
acted as an opponent to the expansion force, caused the con- 
traction. 
From this it would appear that the condition in the con- 
tractile filaments would be the opposite to that of the con- 
=o animal tissue (muscle), inasmuch as in the latter the 
contracted condition is regarded as the active one and the 
elongated as the passive. 
His later researches, he says, have served only to confirm 
the notion that the shortening of the filaments is of a pas- 
sive nature, and due to elasticity, and he is, on this point, more 
than ever inclined to lay great weight upon the peculiar 
thickness of the cuticle, which even in the most completely 
shortened filaments exhibits no appearance of corrugation, 
and consequently must be in the highest degree elastic, so 
that it is able, after the death of the cells, to cause even a 
powerful contraction of the filaments by a transverse corru- 
gation. 
He is also convinced that at least in the lowest animals, which 
possess no muscles, but only a contractile parenchyma, a con- 
dition obtains similar to that observed in the contractile vege- 
table cells. In these animals also irritation causes a momentary 
and death an extreme and permanent contraction, consequent, 
in fact, upon the elasticity of their cuticle, whilst the exten- 
sion and elongation is in them a vital, active process. 
He refers, as a further instance of the same kind, to the 
stems of the Vorticelle, which after death, as upon irri- 
tation, are rolled up, and again acting, extend themselves, 
and, again, to the processes of the Ameba, Actinophrys, 
Diffugia, Arcella, and the Rhizopoda in general, in which the 
elongation is manifestly an active process, whilst the same 
organs, upon being irritated, as after death, contract into 
a ball. 
Experiments with contractile infusoria, which have been 
irritated by an electric current from an induction-apparatus, 
exhibit a perfect resemblance to the phenomena represented 
