To what is ringworm due?
To the presence and growth in the cutaneous structures of a vegetable parasite. Although the disease is contagious, individuals differ considerably as to susceptibility. It is much more common in children than in those past the age of puberty, ringworm of the scalp being limited to the former (rare exceptions), and tinea sycosis being a disease of the male adult.
Until recently the ringworm was thought to be due to but one fungus—the trichophyton; it is now known that there are several forms of fungi, the main forms being the small-spored (microsporon Audouini) and the large-spored (trichophyton). Of this latter there are two main subvarieties—endothrix and ectothrix. The small-spored fungus is found as the cause in the majority of scalp cases; the endothrix also commonly invades the scalp integument. The ectothrix variety is usually derived directly or indirectly from domestic animals, and is chiefly responsible for body-ringworm, and for suppurative ringworm, whether upon the bearded region or elsewhere.
What is the pathology of ringworm?
On the general surface the fungus has its seat in the epidermis, especially in the corneous layer; upon the scalp and bearded region the epidermis, hair-shaft, root and follicle are invaded. The inflammatory action may vary considerably in different cases, and at different times in the same case.
The fungus consists of mycelium and spores. In the epidermic scrapings it is never to be found in abundance, and the mycelium predominates, while in affected hairs the spores and chains of spores are almost exclusively seen, and are usually present in great profusion.
How do you examine for the fungus?
The scrapings or hair should be moistened with liquor potassæ, and examined with a power from three hundred diameters upward.
How is ringworm of the general surface to be distinguished from eczema, psoriasis and seborrhœa?
By the growth and characters of the patch, the slight scaliness, the tendency to disappear in the centre, by the history, and, if necessary, by a microscopic examination of the scales.