176 VEGETABLE PARASITES. 



passages, and by taking the place of swelling and suppuration of 

 the cervical glands, swellings or atrophies of the mesenteric 

 glands, perhaps also of tubercles of the lungs, the bones, and 

 the intestinal canal. The development of the fungus is some- 

 times accompanied by a peculiar odour, like the odour of the 

 urine of a cat, by painful excoriations, and by a swelling of the 

 neighbouring lymphatic glands. A large development leaves behind 

 scars in the skin ; the latter loses its pliancy and imperviousness, 

 and the hair does not grow again, probably on account of the 

 atrophy of the bulb caused by pressure. Oftentimes it is ac- 

 companied by an inconvenient and violent itching, and sickly 

 feeling. The favi spring up again and again, cause the hair of 

 children to fall out in various places, and produce great pain, 

 sickness, and, to some extent, imbecility, thus imparting con- 

 siderable importance to this disease. It is also followed by 

 Pityriasis, Eczema squamosum, and Impetigo, when it lasts long. 

 Ulcers were never observed by Gudden; they may, however, 

 happen, even very deep ulcers, like those which accompany the 

 itch. These may be caused by a secondary action. A very 

 serious addition has to be contended with in the numbers of 

 lice which aggregate on the diseased parts. 



Differential diagnosis. The brariny dust in pityriasis consists 

 of epithelial scales, in dried-up layers or lamellae. The eczema- 

 scales or crusts, which often cover the favus, may easily be 

 distinguished from the latter at a glance. The favus, when it 

 is detached, often depends from its base in the form of a 

 small yellow tubercle. The colourless thin crusts consist only of 

 epithelial scales, lying one above another, and held together by 

 a serous plasma. The yellow crusts are saturated with blood 

 and pus, produced by scratching ; the brown, or earth-gray, crusts 

 consist of decomposed particles of blood. They can be easily 

 recognised by treating them with water and vinegar. 



Pustules of Impetigo are easily distinguished ; they are promi- 

 nent and convex, with a yellow centre, the skin being inflamed 

 all around. Pressure causes them to discharge pus. Their scabs 

 contain no trace of favi, but of dried-up pus-corpuscles and epi- 

 dermal scales. 



Older writers often confounded Achores with Favus. The 

 achores are small yellow pustules and ulcers, which become 

 perceptible when the hair is cut off"; they surround the root of 

 the hair, and appear depressed in the centre. They soon dry up. 



