SCIENCE LETTER FROM PARIS. 29 
selves when unwell. Instinct in the case of man, frequently leads to his ruin ; 
thus the stomach impels him to eat when the interests of good health counsel 
him to moderation or abstinence. Animals select instinctively the food which 
suits them ; man, though not devoid of this instinct, rather disregards it. The 
doctors it seems devote no attention to the tastes of individuals, but which is not 
the less an invaluable guide. Women feel more keenly the want of food than 
men, and further, they do not like the same aliments. However, in the various 
hospices, both sexes are subjected to exactly a common regime. The same fact 
reigns almost everywhere. Again, children hardly weaned, are placed on adult 
dietary, strong meat and wine, which are not only unsuitable, but that they 
dislike. 
Dr. Delaunay from the result of inquiries lays down that a child only likes 
meat when about five years old. He recommends to allow salt, vinegar, etc., 
to those who prefer such condiments. Taste is the best of guides. Instinct aids 
animals also in a sanitary point of view ; they free themselves from parasites by 
rolling in dust, mud, etc. The swallow, when one of its young is attacked by 
vermin, ejects it from the nest to save the rest. When a dog fails in appetite, it 
eats couch grass, which is at once an emetic and a purge. Cats also eat certain 
plants for medicinal ends, and so do sheep and cows. Dogs and horses suffering 
from constipation, will consume fatty substances with avidity, and an animal 
attacked with chronic rheumatism endeavors to lie always in the sunshine. 
Latreille relates that having cut off the antennae of an ant, its comrades 
arrived and covered the wound with a liquid secreted from their mouths ; the 
chimpanzee when wounded staunches the bleeding with leaves or grass; an animal 
with a shattered leg or paw, amputates it with its teeth. Dr. Fredet had a dog 
stung in the nose by a viper; for several days in succession the dog constantly 
plunged its head in a stream till cured. Another dog, crushed by a vehicle, re- 
mained three weeks in a current of water, where it recovered, food being duly 
supplied. Cats also, according to Dr. Delaunay, adopt the cold water cure; one 
has been known to remain during 48 hours under a jet of water. Instinct may 
thus teach us many lessons. 
Sensations have been measured. We know the time which dapses between 
the moment when the skin is touched and the subject feels that pressure. The 
transmission of visual and auditory impressions can also be ascertained. Until 
now it was unknown how long it took for an odor to be perceived. Professor 
Beaunis, and*Dr. Buccola, of Turin, confirms his calculations, affirms that the 
time which separates the excitation from the sensation of a perfume is in hun- 
dredth parts of a second — for ammonia, 37; vinegar, 46; camphor, 50; chloro 
form, 56; mint, 67^; and carbolic acid, 67. The exact moment of perception for 
musk could not be ascertained. It results, that the perception of odors travels 
less rapidly than the sensations of hearing and seeing, and somewhat shorter than 
those of touch. 
By the process known as synthesis, chemistry has been able to re-constitute 
nearly all the substances fabricated by the animal and vegetable organism ; thus 
