No. 2.] CHANGES IN NERVE CELLS. 149 



Experiment V was made for purposes of confirmation simply, 

 and calls for no special mention. 



Perhaps the most active bird that we have is the swallow. 

 Its food consists of insects taken entirely on the wing. Quick, 

 vigorous, purposeful, careful in all its actions, it must require an 

 enormous amount of nervous energy to co-ordinate its countless 

 movements for a long summer's day. All day long, whenever I 

 chance to look up from my work, I see this bird flitting and 

 sailing and circling, fluttering up and swooping down. There 

 is nothing lazy or stupid about the swallows. When their 

 work is done, they play games and fly races ; and with all the 

 energy required for flying, they have enough left to do no end 

 of talking; for their cheerful "zwitschern" is continually in 

 my ears while I write. At one hundred miles an hour, for ten 

 hours, — and I have observed them as early as five o'clock in 

 the morning, and as late as eight at night, — a swallow might 

 cover a distance of one thousand miles in a single day, and day 

 after day. If a bullet of the same weight were to traverse the 

 same distance at the same speed, an enormous explosion of 

 energy would be required, and the living arrow can require no 

 less. 



Accordingly, for Experiment VI, swallows were employed.^ 

 A day was chosen, when weather predictions were favorable, at 

 a time (June 10) when swallows are busiest feeding their young. 

 I reached Goes' Pond in the morning, before a swallow was in 

 sight. At just five o'clock, a large male swallow flitted from 

 the eaves of an ice-house, and, alighting on a telephone wire, 

 began preening his feathers for his morning flight. Within five 

 minutes, his brain and spinal ganglia were in their proper 

 hardening fluids, osmic acid and mercuric chloride. 



Again, at a little before seven, I took my stand by the same 

 pond. Swallows were circling thick. I waited until a few 

 minutes before eight, when all but two, both males, had gone 

 home for the night. One of those flitted too close to my gun, 

 and came down with a broken wing ; and by eight o'clock his 

 brain and ganglia were treated like those of his brother of 

 the morning. I could not, however, help making the note, as 



1 The writer takes pleasure in acknowledging the courtesy of Messrs. E. A. Brackett 

 and Edward H. Lathrop, Commissioners of Fish and Game for the State of Massa- 

 chusetts, in granting the official permit under which these birds were killed. 



