i88 5 .] 
Ignoramus et I gnorabimus . 
46g 
origin. We may often witness among human beings a dis- 
cussion as to whether a sound proceeds from a point to the 
light hand or to. the left, in front or behind. Few of us but 
must on reflection, admit that we have often been deceived 
in attempting to localise a sound. But in all the observa- 
tions which we have made upon cats and dogs, we have 
never seen them thus mistaken. Let anyone scratch with 
ins nafls on the underside of a table at which he is sitting : 
it. there is a cat in the room she will not listen in various 
directions, as if seeking. She will at once turn her eyes 
and ears to the precise spot, even if she cannot have seen 
the least movement of his hand or arm. Had mankind this 
laculty many phenomena would be more accurately traced 
to their sources, and certain superstitions might possibly 
never have arisen. J 
But our greatest shortcoming, both as compared with 
othei animals and with what there is to be known in this 
direction, is in the sense of smell. The scent of the blood- 
hound is commonly held up as a type of acuteness. But 
far more striking is the scent of certain moths. A male 
emperor moth ( Saturnia carpini) recognises the presence of 
a yi r gin female of his species at distances exceeding a mile, 
with woods, fences, hills, or houses intervening. This is far 
moie sti iking than the faculty of the dog, which merely finds 
out the objeCt of its pursuit by following its trail, whilst in 
case of the moth there is no trail to follow. We are apt to 
wonder at the delicacy of the spectroscope, but here are re- 
actions millions of times more sensitive. 
Now we have no science of odours. We detect a few 
of the more prominent, though even there we fail to recog- 
nise their mutual inter-ielations. But had we such an 
odour-sense as the emperor-moth we should be able to 
diagnose animals, plants, minerals, and artificial compounds 
in general by their smell.. We should by this sense be in- 
formed accurately and minutely concerning decompositions, 
fermentations, and putrefactions in dead matter, and con- 
cerning changes, physiological, pathological, and even in 
some cases psychological, in the living. Physics, and still 
more chemistry and biology, would be enriched and modified 
to an extent and in a manner which can be but very imper- 
fectly shadowed forth. 
All these considerations show us how very imperfect and 
fragmentary is the primary material upon which Science has 
to work. Entire categories of phenomena escape us. What 
would be the position of our bookworms if, in the ancient 
treatises in which they delight, letters, words, sentences, 
