EPIPHYTES 689 Leptothrix buccalis. in the stomach of rab- bits, and no trouble caused by its presence. It is supposed to be present most frequent- ly in patients suffering from some gastric dis- ease, organic or other- wise; but this is to be accounted for by the fact that such only vomit, and afford ma- terial or stimulus for investigation. If we remove from our teeth the yellowish white de- posit which collects af- ter the neglect of the tooth brush for several hours, we shall find by microscopic examina- tion, in addition to the detritus of food, a cryp- togamic plant called leptothrix buccalis. It is to be found in all persons, however clean- ly they may be, and forms a large part of the tartar which col- lects about the teeth. It grows with great rapidity after eating sugar, and has been seen in the stomach. Of the parasites of the scalp, the achorion Sch&nleinii is most of all to be dreaded, on account of the deform- ity and disagreeable odor it gives rise to. It produces the disease known as favus, porri- go favosa, or tinea lu- pinosa. The spores first settle upon the epider- mis of the head, and send forth the myceli- um, which penetrates the hair follicles and finally the whole course of the hair itself. The hair becomes pale and lustreless, breaks easily, and is surrounded at its base by concentrical- ly marked yellow and roundish crusts, which smell vilely, and consist of spores and myceli-
- 5 C ^ ! ^ ; 3 um. From one point
this fungus may spread over the whole scalp, producing baldness and scars. Fortunately it Achorion SchoenieLnii. ig of rare occurrence, for a cure is almost impossible. The trico- phyton tonsurans and T. sporuloides also cause baldness when they attack the hair, and the former produces the disease called ring- worm, which is so prevalent in asylums for children. The microsporon Audouini likewise attacks the hair, and the M. mentagrophytes the beard. The only vegetable parasite which is found upon the skin alone is the M. furfur, which is the cause of the eruption known as pityriasis versicolor. Several of the above mentioned species may take root upon the skin as well as the scalp, but they never form a well marked disease like the latter. Various kinds of cryptogamias have been observed with- in the ear, eye, lungs, and nails, but the descrip- tions of them are very defective, and we hardly know where they belong. It is probable that they are species of fungi which have accidentally found a favor- able place for development. ' Man is not the only animal in- fested by the vegetable para- sites. Upon the mammalia it is true that few have been ob- served, but this remains an al- most unexplored field. Many birds bear them in their respi- ratory apparatus, especially the owls, which inhabit damp and shady retreats, frequented by fungi. More curious is it to find within the close-shut cavity of an egg mycelium spreading throughout the contents, and changing them by a peculiar chemical action. This rare phe- nomenon is produced by the admission of spores within the oviduct before the egg shell is formed. Fish are often taken covered with vegetable growths, which impede their motion through the water as the bar- nacles act upon ships. A great many species have also been de- scribed which are found only upon their gills and in the cel- lular tissue. In an aquarium, "tonsurans. whenever an injury happens to any of its inhabitants, the wounded surface is seen at once to be covered with fungoid growths, which often attain a large size. But it is the insect tribe which suffers most from this cause; for their diminutive size is little able to cope with the parasite, which when once fastened increases at their expense, till it exceeds them in size and destroys them. Flies may be seen at certain seasons struggling through the air with long stems attached, the mycelium of which spreading inward stops their breathing tubes. Certain species of sphceria grow within the larvse of insects in China and Australia, and completely mummify them, so that they resemble twigs of wood, from which sprout forth branches. The most
