Preliminary and short reports; the nature of the so-called macroconidia observed on microsporum-infected hairs.

On numerous occasions duriog examination of material taken from suspected cases of tinea capitis, spindle-shaped cells have been noted along the shafts of both infected and uninfected hairs. These cells usually are attenuated at both ends and occasionally are marked by transverse striations. Superficially they bear some resemblance to the macroconidia produced in culture by Microsporuni cenis, and have been identified as such by Appel and Ansell (1). In 3 cases of tinea capitis caused by ill. conis, these investigators reported having found not only the usual mosaic of arthrospores surroundiug the hair shaft but also several "boat-shaped fuseaux". Appel and Ansell considered these bodies to be macroconidia and their record to constitute the first finding of macroconidia on naturally infected hair. However, Montgomery, Flcinlein, and Karpluk (2), in a paper devoted primarily to a summarization of findings in 2,857 cases of tinea capitis, reported having found fuseauxlike bodies in one of their cases. These bodies wore considered to be either "fuseaux or epitholial cells or other formations which have split off from the cortex of the hair itself". Numerous examinations of hairs from normal as well as from infected scalps have led the writer to believe that these spindle-shaped coils are not macroconidia produced by an infecting fungus, hut rather host tissue cells derived from the cuticle of the inner root sheath. The histological relationship of hair to the tissues of the root sheath offers an explanation for the presence of those host cells on epilated hairs (3). The hair cuticle is a single layer of thin, scale-like, imbricated cells, the tips of which arc free and project upwards. The root of the hair is contained within the hair follicle, which is lined with differentiated layers of tissue designated as follows: 1. Outer root sheath 2. Inner root sheath a. Layer of Honle h. Layer of Huxley c. Cuticle The cuticle of the inner root sheath is composed of flat, elongate, non-nucleated cells with downward-projecting free ends and is in intimate contact with the hair cuticle. In fact, the cuticular cells of the hair and of the root sheath interdigitate in such a manner that it is difficult to pluck out a hair without tearing out part of the tissue lining the hair follicle. Figure 1 depicts several spindle-shaped cells associated with a hair which was taken from a normal healthy scalp. That such cells are found associated with normal as well as infected hair should cast doubt upon their allegedly mycotic origin. It should be noted in addition that these "f useaux" have been observed not only in hair invaded by ill. ceeis hut also in infections caused by M. Audonini , as shown in figure 2. The latter fungus, as a rule, forms macroconidia rarely and then under such special nutritive conditions that the formation of such spores on hair is extremely unlikely. Corroborative evidence for the animal derivation of the so-called "fuseaux" was obtained by comparing the dimensions of these cells with those of macrocoaidia taken from