1885. ] Psychology. 909 
represent the dim bands of the resting muscle, while the singly 
refracting light bands of the resting muscle disappear completely 
during maximal tetanus, being- absorbed apparently by the doubly 
refracting substance of the dim band. When the tetanus was not 
maximal some of the singly refracting substance was still found 
in the contracted fiber. 
The results given go to support Englemann’s theory of muscle 
contraction, according to which the shortening of the contracted 
fiber is owing to the absorption by imbibition of the singly re- 
fracting substance of certain ultimate elements in the doubly re- 
fracting substance, thus becoming spherical during the act and 
decreasing in diameter. 
PSYCHOLOGY. 
Do MONKEYS INVARIABLY LEARN by EXPERIENCE ?—Some time 
ago I read a statement to the effect that monkeys were unable to 
learn by experience, a particular in which they were said to differ 
from cats. The experiment suggested was to show the animal its 
reflection in a mirror, and after a time to repeat the process and 
: observe whether it would be deceived a second time. I have 
never had the opportunity to try the experiment on monkeys, 
though I am told, on tolerably good authority, that a monkey can 
never Satisfy itself that there is not another monkey behind the 
glass. But my acquaintance with cats is somewhat larger, and I 
find that, after once thoroughly investigating the subject, a cat 
which has reached an age of discretion takes no further interest in 
its cwn reflection. The question in my mind is: if a monkey can- 
not learn by experience, how can it learn? for it seems to me 
that almost every means of learning can be reduced to some 
form of experience, or to something that is practically the same 
thing —W. H. Frost, Brown University. 
in his brains. Heis very sagacious and knowing, and only 
seems to lack the power of speech to show that sensible ideas run 
through his head. He likes to leap from a stump into my arms 
as I am on horseback, and go off with me at a full gallop. One 
day a lot of pigs got out of their enclosure through a little hole 
at the apex of an acute angle, or corner, of the fence. This angle 
widened into the garden where the pigs were not tolerated. As 
soon as “ Trip” saw them he went after them to get them out. 
They fled before him into this angle and began, slowly, of course, 
to make their way through. As soon as he saw them all within 
the angle, he stopped before its widest opening—the base—and 
intently watching, waited until the last one had crawled back — 
into its proper enclosure. He seemed to understand that if he 
made a dash at them they would turn around and rush back into 
