Passing to the fleas, the most important and truly parasitic form is the chigoe or gigger (_Pulex penetrans_). This abounds in tropical America and the West Indies. The female insects only attack man, and this they do for the purpose of securing a lodgment for their offspring. They attack especially the soles of the feet, between the toes and near the nails. In bad cases the whole of the foot becomes affected. After the insect has penetrated the skin its body swells enormously and becomes a mere bag of eggs. This swelling causes active inflammation, which terminates in suppuration and the formation of open ulcers. The chigoe also attacks various animals. In addition to the common flea (_P. irritans_) other species infesting animals are said to attack man occasionally. As regards those degraded types of insects known as lice I can only afford space to remark that five species have been recognised as human. These are the head-louse (_Pediculus capitis_); the louse of the eyelids (_P. palpebrarum_); the clothes-louse (_P. vestimenti_); the distemper louse (_P. tabescentium_); and the pubic louse (_P. inguinalis_). The distress these creatures occasion is only fully known to physicians who deal with the obstinate cutaneous affections caused by their presence (_Phthiriasis_). Some of the lice found on negroes and Greenlanders are regarded as distinct varieties. Lice are abundant on animals, and some of the species are apt to transfer themselves from one host to another. Thus the _Ornithomyia avicularis_ of cage birds has been found on man, whilst one or more of the numerous species infesting the common fowl are, by transfer, apt to produce a severe phthiriasis in the horse. The lice of the fowl belong to the genera _Leipurus_, _Liotheum_, _Menopon_, _Philopterus_, _Goniodes_, and _Goniocotes_. The unsuitableness of man’s person as a habitation for bird-lice should, however, check the fear which many persons have of handling fresh-killed poultry and game birds. Poultry lousiness in man is probably impossible from this source.