422 



THE SKIN 



tubercle bacilli are exceedingly scarce. Inoculation of a guinea-pig 

 will probably give positive results with the tubercle bacillus. The 

 leprosy bacillus is noninoculable for experimental animals. 



Anthrax and glanders cause skin lesions which can only be surely diagnosed 

 culturally or by animal inoculation. 



Plague bacilli may be isolated from the primary vesicles appearing at the site of 

 the flea bite. 



Tropical phagedaena is thought by some to be due to a sort of diphtheroid or- 

 ganism. The organisms of Vincent's angina may cause tropical ulcer. Herpes 

 zoster has been reported by Rosenow as most probably due to a streptococcus with 

 special affinity for the ganglia and posterior roots. 



The skin diseases due to fungi are discussed under that section. Of the skin 

 affections caused by animal parasites, ground itch is the most important. This is a 

 form of dermatitis due to the irritation set up by the hook-worm larvae penetrating 

 the skin of the foot and leg. 



The Sarcopsylla penetrans or jigger (sand flea) is an important agent in ulcera- 

 tions about the foot. 



Certain acarines cause skin lesions, as is also the case with the larvae of certain 

 flies. 



'fhe itch mite (Sarcoptes scabiei) is an important animal parasite of the skin. 



The various lice, fleas and bedbugs are well understood as causes of skin irrita- 

 tion. 



Filarial infections are also important especially the ulcers of the 

 Guinea-worm, Calabar swellings of F. loa, the cystic tumors of F. 

 volvulus and the varicose groin glands and elephantiasis of F. bancrofti. 



Leeches, as H. ceylonica, may cause serious ulceration. 



Oxyuris may cause a severe irritation about the region of the groin and inner 

 surfaces of the thigh, and especially about the vulvar region of female children. 



Gnathostomum siamense, a nematode with two lip-like structures and spine- 

 like appendages covering its anterior one-third, has been found once in a tumefac- 

 tion of the breast. 



Plerocercoid larvae of Dibothriocephalidae have been found in the subcutaneous 

 tissues. 



Certain skin diseases, as Oriental sore and yaws, are protozoal in origin. The 

 cutaneous lesions of uta or espundia are now known to be caused by a Leishmania 

 as well as Oriental sore. These affections in the Central and South American 

 countries are now known as American leishmaniases. 



Dew itch or foot itch is caused by the penetration into the skin about the toes of 

 the strongyloid encysted larva of the hook-worm. 



