48 SCIENCE IN SHORT CHAPTERS. 



factory nerves beyoiid the central hemispheres goes on ex- 

 tending more and more, and the relative magnitude of 

 the terminal ganglia or olfactory lobes increases in similar 

 order. 



We have only to omit the nasal bones and nostrils, to 

 continue this forward extrusion of the olfactory nerves and 

 their bulbs and branches, to coat them with suitable sheaths 

 provided with muscles for mobility, and we have the anten- 

 nae of insects. I submit this view of the comparative ana- 

 tomy of these organs as my own speculation, to be taken 

 for what it is worth. 



There is no doubt that the antennae of these creatures 

 are connected by nerve-stalks with the anterior part of 

 their supra-oosophageal ganglia, i.e., the nervous centres 

 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 difficult to con- 

 ceive the possibility of what we actually see him do. As 

 an example, I may describe an experiment I made upon a 

 bloodhound of the famous Cuban breed. He belonged to 

 a friend whose house is situated on an eminence command- 

 ing an extensive view. I started from the garden and wan- 

 dered 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 dif- 

 ferent track. The bloodhound was set upon the begin- 

 ning of my track. I watched him from a window gallop- 

 ing rapidly, and following all its windings without the least 

 halting or hesitation. It was as clear to his nose as a 

 gravelled path or a luminous streak would be to our eyes. 

 On his return I went down to him, and without approach- 

 ing 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.* 



* What did he smell? Was it an emanation from the soles of my 

 feet? If so, how did this aura get through the soles of my boots, 



