Tyndall Phenomenon

TYNDALL PHENOMENON, a phenomenon, or effect, consists in the fact that a bright beam of light passing through certain transparent bodies and viewed in a direction perpendicular to the path of the light rays is seen in the corresponding transparent body as a certain cloudy strip, which at first glance resembles the light strip obtained by fluorescence. The Tyndall effect is observed mainly in colloidal solutions, and, as more thorough investigations have shown, the light emitted in the direction perpendicular to the path of the rays turns out to be polarized light. A deeper study of the Tyndall phenomenon under the microscope was carried out by Siedentopf and Szigmondi, who showed that the scattering of light by colloidal solutions of gold or platinum depends on the diffraction of light on individual grains of the colloid. These grains can be visible under the microscope as luminous points, even if their size is significantly smaller than the size of bodies that can be visible under the microscope. On this principle, Siedentopf and Szigmondi founded a new method for studying ultramicroscopic particles, so-called ultramicroscopy. Later extensive investigations by Cabannes, Rayleigh, and others showed that the phenomenon of diffraction can also occur near the molecules of solid and liquid substances that do not have a colloidal character. Due to the smallness of the molecules, the amount of scattered light in this latter case is significantly less than in colloidal solutions. The T. f. can be mixed with the phenomenon of fluorescence, however, between these two phenomena there is a sharp difference; manifesting itself first of all in the fact that with the Tyndall phenomenon, simple scattering of light is observed, not accompanied by a noticeable change in the wavelength of the incident light. With fluorescence, on the contrary, a sharp change in wavelength occurs (Stokes' law), and the light emitted during fluorescence has a longer wavelength than the light causing fluorescence. Light during fluorescence is not polarized light, whereas light during the T. f. is polarized. The T. f., specifically the measurement of the intensity of light scattered by suspended particles (Tyndall light), is the basis of nephelometry (see). The Tyndall phenomenon explains the coloration of many bodies. For example, colloidal solutions of gold, containing in a suspended state ultramicroscopic particles of metallic gold, show coloration phenomena depending on the fact that light rays of different wavelengths are diffracted in different ways on gold particles.

p. Lazarov. TINEA (Latin-mole, French teignes-molds), a name formerly applied to various kinds of peeling processes on the hairy part of the head; later the word T. began to denote exclusively fungal diseases of the skin, mainly trichophytia. At present, in the generally accepted dermatological nomenclature, the name T. is applied only in relation to some tropical dermatomycoses: tinea imbricata, cruris, and others. T. cruris is a dermatomycosis similar to the so-called circumscribed eczema (eczema marginatum Hebrae), caused by the fungus Epidermophyton inguinale Sabouraud (see Epidermophytia). T. cruris is very widespread in tropical countries, and the Trichophyton cruris Castellani and Trichophyton Perneti isolated there from these lesions are apparently identical with Trichophyton inguinale Sabouraud. T. imbricata (Latin - scale-like T.) is a fungal disease of human skin, occurring mainly in Brazil, in South India and South China, on the Philippine and Caroline Islands, in New Guinea, and elsewhere. The disease is caused by a variety of trichophyton first discovered by Manson. The fungus usually affects hair follicles. The lesion can be localized on the whole body except for the hairy skin of the head and face; peculiar multiple concentric peeling ring-shaped plaques arise. Treatment is the same as for superficial trichophytia of smooth skin (see Trichophytia). The disease is mainly contracted by natives. T. pedosa is a rare affection of the hair described by Cheatle and Morris (1879); on the hair shaft, node-like thickenings similar to those in piedra (see Trichophytosis) are formed. Unlike trichorrhexis nodosa (see Trichorrhexis), these nodes represent not a split hair, but consist of light-refracting bodies, the true nature of which is unknown.

L. Mashkilelis. THIOSINAMIN, Thiosinamin, allylthiocarb-amide, allylthiourea, /NH₂ cs ⁴NH.CH,.CH.CH_a Colorless crystals with a weak, garlic-like odor, bitter taste, melting at 74°. Soluble in water, alcohol, and ether. T. causes impregnation of scar tissue with serous exudate and accumulation of leukocytes, which leads to softening and loosening of the scar tissue. Side effects: burning at the injection site, rash, increase in body temperature, especially in tuberculosis patients. Applied externally for scars after burns, for lupus, for postoperative adhesions, strictures of the esophagus, auditory canal, etc. Prescribed internally in doses of 0.03-0.1 for articular rheumatism. Subcutaneously and intramuscularly in a 10% glycerin solution for the removal of scar tissue. It is part of fibrolysin (see).