68 JENNER. 



taste for music, being able to play on the flute and violin, and sing 

 his own verses with considerable taste and feeling. Such was the 

 attachment of Jenner's friends to him at this period of his career, 

 and so highly did they value his amusing and interesting conversa- 

 tion, that, when he had called at their houses, either as a visitor or 

 in his professional capacity, they would accompany him, on leaving, 

 many miles on his way home, and this too, often at midnight, in 

 order that they might prolong the pleasure derived from his com- 

 pany and conversation. 



Although Jenner's time was chiefly occupied with his profess iona 

 duties, he still kept up a constant and regular correspondence 

 with his friend John Hunter on different scientific subjects. He 

 managed also to find leisure to institute many experiments and 

 observations in natural history, one of the results of which was his 

 account of the Cuckoo, a most carefully elaborated essay, and which 

 has always been considered as a model of accurate observation. 

 This paper was read to the Royal Society on the 10th of March, 

 1788, and printed in their ' Transactions.' It explained the habits 

 of this curious bird very satisfactorily, and its publication at once 

 secured the author a considerable reputation as a Naturalist. As 

 this paper appears not to be very generally known, the following 

 account taken from it may be interesting : 



" The cuckoo furtively deposits her egg in the nest of another 

 bird ; it is done not that her offspring may be a sharer of the care 

 of the foster-parent, but that it may engross it entirely to the total 

 destruction of its own natural offspring. A perversion of all the 

 maternal instincts is a most remarkable result of this vicarious 

 incubation. The hedge-sparrow, or other birds whose nests have 

 been visited by the cuckoo, actually sometimes eject their own eggs 

 to make room for the new guest ; but it occasionally happens that 

 this is not done ; the eggs are not disturbed, and the process of 

 hatching is allowed to go on regularly, and the young sparrows and 

 the cuckoo emerge from the shell about the same time. This event, 

 when it is permitted to happen, does not at all improve the con- 

 dition of the former; on the contrary, it only exposes them to 

 greater sufferings. The size of the egg of the cuckoo does not vary 

 much from that of the bird in whose nest it is deposited. When 

 the young sparrow, therefore, and the intruder first come into life, 

 they are pretty much on an equality ; but unhappily for the foster- 

 brethren, this equality does not last long: the cuckoo's growth 

 rapidly outstrips that of his companions, and he immediately ex- 

 ercises his new powers with abundant selfishness and cruelty. By 

 a singular configuration of his own body he contrives to lodge his 

 companions, one by one, upon his back, and then scrambling up the 

 sides of the nest, he suddenly throws them from their seat, and 

 completely ejects them from their own home to become food for 

 worms. There is reason to believe that the unnatural parent is 



