GOLIATH ARATOO. Micruglussvm aterrimum. 



This substance is found very largely in most of the Parrot tribe, and I well remember 

 getting my coat powdered like that of a miller from playing with the great white Cockatoo 

 in the Zoological Gardens of Dublin. Many other birds, such as the vultures, possess 

 this curious powdery substance, whose office is rather doubtful. The powder is produced 

 from the formative substance of the quill, which, instead of being developed into shaft 

 and web, as in the case of the perfect quills, dries up and is then thrown off in a dusty 

 form. The imperfect quill-feathers can generally be seen intermixed with the rest of the 

 plumage when the Cockatoo bends down its head or plumes itself, and the white substance 

 may be seen in the open ends of the imperfect quills, or lying thickly about them. In 

 the case of the vultures it is thought to be given for the purpose of keeping their skin and 

 plumage undefiled by the putrid animal substances on which those unclean and useful 

 birds feed, but as it is found in equal plenty on the Cockatoos, than who no cleaner 

 feeding or more fastidious birds exist, it is evident that it must serve some purpose that 

 is common to these two dissimilar species. Very little structure is found in this dust 

 when placed under the microscope, but with the aid of the polarizer I have made out 

 several well-marked hexagonal cells. 



