BIRDS IN GENERAL. 15 



channel of the ureters, which may be distinguish- 

 ed from the coats of the kidneys by their white- 

 ness. This milky substance they have in greater 

 plenty than the more thin and serous part ; and 

 it is of a middle consistence, between limpid 

 urine and the grosser parts of the faeces. In 

 passing through the ureters, it resembles milk 

 curdled or lightly condensed; and being cast 

 forth easily, congeals into a chalky crust." 



From this simple conformation of the animal, 

 it should seem that birds are subject to few dis- 

 eases ; and in fact they have but few. There is 

 one, however, which they are subject to, from 

 which quadrupeds are in a great measure exempt : 

 this is the annual moulting which they suffer ; for 

 all birds whatsoever obtain a new covering of 

 feathers once a-year, and cast the old. During 

 the moulting season, they ever appear disorder- 

 ed ; those most remarkable for their courage then 

 lose all their fierceness, and such as are of a weakly 

 constitution often expire under this natural ope- 

 ration. No feeding can maintain their strength ; 

 they all cease to breed at this season ; that 

 nourishment which goes to the production of the 

 young, is wholly absorbed by the demand requir- 

 ed for supplying the nascent plumage. 



This moulting time, however, may be artificially 

 accelerated, and those who have the management 

 of singing birds frequently put their secret in 

 practice. They enclose the bird in a dark cage, 

 where they keep it excessively warm, and throw 

 the poor little animal into an artificial fever : this 

 produces the moult ; his old feathers fall before 



47 



