12 SCIENCE IK SHOUT CHAPTERS. 



these insects converse with each other by movements of the 

 antennae, and he has given to the signs thus produced the name 

 of *' antennal language." They certainly do communicate 

 information or give orders by some means ; and when the 

 insects stop for that purpose, they face each other and execute 

 peculiar wavings of these organs that are highly suggestive of 

 the movements of the old semaphore telegraph arms. 



The most generally received opinion is that these antennae 

 are very delicate organs of touch, but some recent experiments 

 made by Gustav Hansen indicate that they are organs of 

 smelling or of some similar power of distinguishing objects at 

 a distance. Flies deprived of their antennae ceased to display 

 any interest in tainted meat that had previously proved very 

 attractive. Other insects similarly treated appear to become 

 indifferent to odors generally. He shows that the develop- 

 ment of the antennae in different species corresponds to the 

 power of smelling which they seem to possess. 



I am sorely tempted to add another argument to those 

 brought forward by Hansen viz. that our own olfactory nerves, 

 and those of all our near mammalian relations, are cuiiously 

 like a pair of antennae. 



There are two elements in a nervous structure, the gray and 

 the white ; the gray or ganglionic portion is supposed to be 

 the centre or seat of nervous power, and the white medullary 

 or fibrous portion merely the conductor of nervous energy. 



The nerves of the other senses have their ganglia seated 

 internally, and bundles of tubular white threads spread out- 

 ward therefrom ; but not so with the olfactory nervous appara- 

 tus. These present two horn-like projections that are thrust 

 forward from the base of the brain, and have white or medul- 

 lary stems that terminate outwardly or anteriorly in ganglionic 

 bulbs resting upon what I may call the roof of the nose ; these 

 bulbs throw out fibres that are composed, rather paradoxically, 

 of more gray matter than white. In some quadrupeds with 

 great power of smell, the olfactory nerves extend so far for- 

 ward as to protrude beyond the front of the hemispheres of 

 the brain, with bulbous terminations relatively very much larger 

 than those of man. 



They thus appear like veritable, antennae. In some of our 

 best works on anatomy of the brain (Solly, for example) a 

 series of comparative pictures of the brains of different animals 

 is shown, extending from man to the cod-fish. As we proceed 

 downward, the horn-like projection of the olfactory nerves 



