48 THE POPULAR SCIENCE MONTHLY, 



AVe bave only to omit the nasal bones and nostrils, to continue 

 this forward extrusion of the olfactory nerves and tbeir bulbs and 

 branches, to coat them with suitable sheaths provided with muscles 

 for mobility, and w^e have the antennae of insects. I submit this view 

 of the comparative anatomy of these organs as my own speculation, to 

 be taken for w^hat it is worth. 



There is no doubt that the antennae of these creatures are connected 

 by nerve-stalks w4th the anterior part of their supra-oesophageal gan- 

 glia i. e., the nervous centers corresponding to our brain. 



But what kind and degree of power must such olfactory organs 

 possess ? The dog has, relatively to the rest of his brain, a much 

 greater development of the olfactory nerves and ganglia than man has. 

 His powers of smell are so much greater than ours that we find it dif- 

 ficult to conceive the possibility of what we actually see him do. As 

 an example, I may describe an experiment I made upon a blood-hound 

 of the famous Cuban breed. He belonged to a friend whose house is 

 situated on an eminence commanding an extensive view. I started 

 from the garden and wandered about a mile away, crossed several fields 

 by sinuous courses, climbing over stiles and jumping ditches, always 

 keeping the house in view ; I then returned by quite a different track. 

 The blood-hound was set upon the beginning of my track. I watched 

 him from a window galloping rapidly, and following all its windings 

 without the least halting or hesitation. It was as clear to his nose as 

 a graveled path or a luminous streak w^ould be to our eyes. On his 

 return I went down to him, and without approaching nearer than five 

 or six yards he recognized me as the object of his search, proving this 

 by circling round me, baying deeply and savagely though harmlessly, 

 as he always kept at about the same distance. 



If the difference of development between the human and canine 

 internal antennae produces all this difference of function, what a gulf 

 may there be between our powers of perceiving material emanations 

 and those possessed by insects ! If my anatomical hyj^othesis is cor- 

 rect, some insects have protruding nasal organs or out-thrust olfactory 

 nerves as long as all the rest of their bodies. The power of movement 

 of these in all directions affords the means of sensory communication 

 over a corresponding range, instead of being limited merely to the 

 direction of the nostril-openings. In some insects, such as the plumed 

 gnat, the antennae do not appear to be thus movable, but this want of 

 mobility is more than compensated by the multitude of branchings of 

 these wonderful organs whereby they are simultaneously exposed in 

 every direction. This structure is analogous to the fixed but multi- 

 plied eyes of insects, which, by seeing all round at once, compensate 

 for the want of that mobility possessed by others that have but a single 

 eyeball mounted on a flexible and mobile stalk ; that of the spider, for 

 example. 



Such an extension of such a sensory function is equivalent to liv- 



