52 HISTORY OF THE 



tional argument to those previously urged against 

 the hypothesis advanced by Dr. Jenner, that a 

 premature change uniformly takes place in the 

 physical condition of the reproductive system of 

 those birds which abandon their progeny to de- 

 struction ; for it is in the highest degree impro- 

 bable, that an organic change, sufficient to in- 

 duce a total alienation of parental affection, a 

 change, let it be remembered, which, in every 

 observed case, has been found to proceed gra- 

 dually, should so suddenly succeed to the ex- 

 tremely active state of the system indicated by 

 the recent production of prolific eggs. The 

 simultaneous departure of both sexes also, when 

 they desert their offspring, which, as far as my 

 own researches extend, appears to occur with 

 great regularity, is too remarkable a fact to be 

 accounted for on a principle so uncertain in its 

 operation as that maintained by Dr. Jenner. 



A belief, represented by Dr. Fleming, in his 

 Philosophy of [Zoology, vol. II. pages 72 — 3, 

 as prevalent throughout Scotland, that swallows 

 are sometimes found torpid in their nests, has 

 most Hkely originated in the discovery of the 

 forsaken young of the swallow and house-mar- 

 tin, (for both species are termed swallows indis- 

 criminately by the multitude,) in a perishing 

 condition, or dead. 



