16 BRITISH BIRDS. 



Royal College of Surgeons Museum a specimen of a sebaceous 

 " horn " on the head of a mouse. There are also in the 

 museum a few specimens of bony horn-like growths in 

 birds arising from bone, and in a Thrush {Turdus musicus) 

 there is a tumour on the skull, said to be sebaceous in 

 origin, but as there are no sebaceous glands in this posi- 

 tion such a diagnosis seems improbable. There is, 

 however, a specimen of a pigeon with a tumour on each 

 side of the pygostyle which may have originated in the 

 oil-gland, but it is not a horny excrescence. 



