CHAPTER II 



Classification of Fungi 



FUNGI are microscopic members of the plant kingdom. They are 

 included in the phylum of Thallophyta, in which there is no differen- 

 tiation into roots, stem and leaves. There is further division into the orders 

 of Algae and Fungaceae. Since the latter do not contain chlorophyll, they 

 are unable to carry on photosynthesis. Fungaceae are divided into Bacteria, 

 true fungi and Myxomycetes. The true fungi are divided into four sub- 

 classes; the most important subclass consists of Hyphomycetes, or fungi 

 imperfecta which include practically all the fungi pathogenic to human 

 beings. 



There have been many attempts further to classify and arrange the fungi 

 which cause ringworm. Most of those who have studied the subject are 

 dissatisfied with the existing subdivisions but realize that a botanic solution 

 of the problem is at present impossible. It is usual to classify the fungi im- 

 perfecti which cause ringworm as dermatophytes. Sabouraud pointed the 

 way to a purely clinical approach, and his classification of the superficial 

 dermatophytes has been widely used. We believe that a modification of 

 Sabouraud's arrangement (to suit the flora in this country) is sufficient for 

 all who are not essentially botanists. 



In Sabouraud's classification, fungi having small spores in which the ele- 

 ments are found in mosaic arrangement and in profusion on the surface of 

 the hair are known as Microspora. The next group comprises Trichophyta, 

 divided into endothrix, which invades the hair shaft with the formation of 

 large spores in linear arrangement, and ectothrix, which forms chains of 

 spores external to the hair. The endothrix micro-organisms are usually not 

 inoculable into laboratory animals, whereas the ectothrix fungi are often 

 pathogenic for them. The genus Achorion includes only one common path- 

 ogen, the cause of favus. It may be well to drop this term and include 

 Achorion with the endothrix Trichophyta. The term "Epidermophyton" 

 denotes lack of invasion of a hair follicle. 



