ve been known to express pleasure through the agency of the
smile. And, in the case of certain monkeys, the action of the facial
muscles was accompanied by cachinnatory sounds.

"Tom," a capuchin monkey of the St. Louis, Missouri, zooelogical garden
(Fair Grounds), was quite a noted "laugher," and his facial expressions
as well as the sounds he uttered were so evidently laughter, pure and
simple, that the most casual observer was able to recognize them as
such.

"Stranger," a half-bred spaniel belonging to my kennel, invariably
expressed pleasure with smiles. The action of the facial muscles, as
well as the facial expression engendered by this action, was widely
different from like phenomena when the dog showed his teeth in
anger.[45]

[45] Compare Darwin, _Expression of the Emotions_, p. 120.

Young chimpanzees chuckle and smile when one they love returns to them
after an absence of some little time. Their eyes sparkle and grow
bright, while very evident and easily recognized smiles flit over their
countenances.[46]

[46] Martin, _Natural History of Mammalia_, Vol. I. pp. 383, 410;
quoted also by Darwin, _loc. cit. ante_.

Young orang-utans likewise chuckle and grin when tickled, and, as
Wallace observes, give expression to unmistakable smiles. "Dr.
Duchenne--and I cannot quote a better authority--informs me that he kept
a tame monkey in his house for a year; and when he gave it, during
meal-times, some choice delicacy, he observed that the corners of its
mouth were slightly raised; thus an expression of satisfaction,
partaking of the nature of an incipient smile, and resembling that often
seen on the face of man, could be plainly perceived in this animal."[47]

[47] Darwin, _loc. cit. ante_, p. 133.

A dog belonging to Mr. Henry Barklay, of Paducah, Kentucky, not only
smiles when pleased, but also gives utterance to an unmistakable
chuckle. When I first saw and heard this manifestation of delight, I
thought that the animal had been taught the accomplishment; his master
assured me, however, that such was not the case, that both the smile and
the chuckle were natural and inborn traits of the dog.

I think it hardly necessary to give more data on this point; suffice it
to say that it is a fact beyond dispute that certain monkeys and dogs
are "laughing animals," and that man is _not_ the only animal that
expresses emotion through the agency of the smile and laughter!

On one occasion during very hot we