274 BACTERIOLOGY FOR NURSES 



than certain other forms in that they penetrate to the underlying 

 tissue instead of vegetating on the surface layer of the skin. The 

 infection probably commences first in the epidermis surrounding 

 the hair bulb and from thence it spreads into the bulb and up 

 into the hair substance. The organisms may be readily seen by 

 removing a hair with the bulb attached and placing it in a drop of 

 sodium or potassium hydroxide solution under a coverslip. Ex- 

 amined with the microscope, enormous numbers of interlaced 

 threads and spores may be seen lying within the bulb. 



Favus. The disease is contagious and is produced by Achorion 

 schoenleinii, a mold discovered by Schoenlein in 1839. The organ- 

 ism grows more slowly than that producing ringworm. It affects 

 both the hairy and smooth parts of the body and attacks most 

 frequently the skin of persons whose vitality is low. Usually 

 the disease appears on the scalp, but may attack any portion of 

 the skin or even the mucous membranes. Growth appears as 

 tiny round sulphur-yellow disks with a cup-like depression pierced 

 in the center by a hair. The spores penetrating into the hair 

 follicles cause by the density of their growth such pressure upon 

 the tissue beneath that the vitality of the hair is impaired. Fre- 

 quently the hair becomes invaded, the shaft especially being 

 affected. The chief feature of the disease, however, is the destruc- 

 tion of the epithelial cells of the hair follicles, resulting when re- 

 covery takes place in the formation of cicatricial tissue. 



Pityriasis Versicolor. The organism giving rise to this condi- 

 tion was discovered by Eichstedt in 1846 and later named Micro- 

 sporon furfur. It appears to be less parasitic than the fungus of 

 ringworm and flavus and attacks only the superficial layer of the 

 skin. The growth appears as a scaly eruption, varying in color 

 from a creamy yellow to a reddish brown. It occurs chiefly in 

 persons living under uncleanly conditions or in those who have a 

 tendency to profuse perspiration. Several of the lower animals 

 are susceptible, especially the cat. 



Sporotrichosis. The disease, which is characterized by a swell- 

 ing of the lymphatics and a chronic ulcerative condition, was shown 

 by Schenk in 1898 to be due to another member of the fungi 



