the time of birth. Taste probably is better perceived, yet some
newborn babies are said to suck a two per cent solution of quinin as
eagerly as milk, though stronger solutions are distasteful. According
to the best available information a young infant can detect the
difference between a sweet, bitter, sour, or salty taste only when
the tests are made with a solution possessing the quality in question
to a marked degree. It is common knowledge that babies cheerfully
suck the most tasteless objects, and it is not improbable that at
first the reaction depends upon the temperature of the object and the
feeling it creates in the mouth.

The moment it is born, a baby perceives pressure if its skin is
touched. To this sensation, however, some parts of the body are much
more sensitive than others; the tongue and lips are most sensitive of
all. Heat and cold are probably perceived more acutely by infants
than by adults; to pain, on the other hand, babies are less
sensitive. An infant is aware of the movements of its own muscles,
and also appreciates a change from one position to another, as
experienced nurses know very well, and on that account carefully
avoid keeping a baby on one side continuously.

The vast majority of movements performed by young infants are reflex
acts, that is, the cerebrum, the part of the brain with which
thinking is done, is not concerned with their performance. Of these
reflexes the most notable are sucking and swallowing, but sneezing,
coughing, choking, and hiccoughing may also be observed; stretching
and yawning have been recorded in several instances, even during the
first days of infant life. None of these movements, we must remember,
are produced consciously; the baby cannot reason and does not
recognize anyone, even its mother.