B. G. Jefferis and J. L. Nichols

“ The black appearance is really due the accumulation of dirt which gets under the edges of the skin of the enlarged sweat glands and cannot be removed in the ordinary way by washing, because the abnormal, hardened secretion of the gland itself becomes stained. These insects are so lowly organized that it is almost impossible to satisfactory deal with them and they sometimes cause the continual festering of the skin which they inhabit. ”

“ These creatures live on the sweat glands or pores of the human face, and owing to the appearance that they give to the infested pores, they are usually known as "black-heads." It is not at all uncommon to see an otherwise pretty face disfigured by these ugly creatures, although the insects themselves are nearly transparent white. ”