Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/287

 VEGETABLE.] vegetate by means of its own intrinsic chlorophyll was finally established in 1878 by the experiments of Geddes on Convoluta Schultzii, Schm. He found that the analysis of the gas given off by these green animals, under the influence of direct sunlight, &quot; yielded from 45 to 55 per cent, of oxygen.&quot; The discovery of these vegetating animals directed fresh attention to chlorophyll-bearing animals, with much result. The nature and functions of the yellow cells of radiolarians had long been an unsolved enigma. Haeckel had detected in them in 1870 the pre sence of starch, and regarded them as stores of reserve material. Cienkowski, in the following year, contended for their algal nature without finally deciding the question, i and without perceiving the significance such organisms would have in the economy of the radiolarian. Much suggestive observation followed by the Hertwigs, Brandt, Entz, Korotneff, Lankester, Moseley, and others on similar bodies in various organisms ; but the subject remained in uncertainty till its reinvestigation by Brandt, and sim ultaneously and much more conclusively by Geddes, finally supplied the solution of the difficulties. After confirming HaeckePs discovery of the presence of starch, and the observations of Cienkowski, Brandt, and others on the survival of the yellow cells after the death of the radiolarian, and extending his observation to various other organisms, Geddes demonstrated the truly algal nature of these cells from their cellulose walls, the identity of their yellow colouring-matter with that of diatoms, and the evolution of oxygen (in some instances, such as Ant km Cereas, very copiously) under the influence of sunlight. It was pointed out that the animal protoplasm investing these starch-producing cells (and containing amylolytic ferment) must obtain by osmosis its share of the dissolved starch, and that benefit must accrue to the animal from thedigestion of the dead bodies of the algao. The evolution of oxygen during sunshine into the surrounding animal protoplasm is a respiratory function fittingly compared to that per formed by certain stationary deposits of haemoglobin. On the other hand the carbonic acid and nitrogenous waste produced by the animal cell is the nutritive return made to the alga, which in removing them performs an intracel- lular renal function. The young gonophores of Vcldlit, after budding off from the parent, start in life with a pro vision of algte, and in this respect bear interesting resem blance to the function performed by the hymenial-gonidia of lichens described above. The physiological relations are summed up as follows : &quot; Thus, then, for a vegetable cell no more ideal existence can be imagined than that within the body of an animal cell of sufficient active vitality to manure it with abundance of carbonic anhydride and nitrogenous waste, yet of sufficient transparency to allow the free entrance of the necessary light. And, con versely, for an animal cell there can be no more ideal existence than to contain a sufficient number of vegetable cells, constantly removing its waste products, supplying it with oxygen and starch, and being digestible after death.&quot; The completeness of the case thus established for a symbiotic mode of life marks one of the most interesting and impressive chapters in the history of the biological relations between animals and plants. A re-discussion of the subject, largely historical and controversial, but with excellent bibliography, has been lately furnished by Brandt, and more recently a further contribution has been made by Oscar Hertwig, who repeats the views of preceding investigators and goes on to speculate as to the nature of symbiosis and its general relations with other modes of life. 1 (a. MU.) 1 Schultzc, Beitr. zur Xaturges. &amp;lt;!. TurMlarien, 1801. Lankestcv, &quot;Abstract of a Report on the Spectroscopic Examination c f certain Animal Substances,&quot; .lout: of Anat., iv. 1870; Id., U 0n Ilaliphysema&quot; Quart. Jour. Microscop. Sci., 1870, and &quot; On the Chlorophyll Corpuscles and Amyloid Deposits of Sponyilla and 269 PARASITISM ix MEDICINE. Only a limited number of the parasitic diseases of man are included in the present article. Under TAPEWORM will be found all that medically relates to that important parasitic group, and under SCHIZOMYCETES will be dis cussed the significance of the parasitic micro-organisms (Bacterium, Bacillus, Spirillum, Vibrio, Arc.) in morbid pro cesses, and particularly in the infective diseases. There fall to be considered here (1) the skin-diseases due to filamentous fungi, (2) a peculiar disease called &quot;actino- mycosis,&quot; primarily affecting cattle, (3) the itch, and (4) certain diseases caused by various species of nematodes, and one disease caused by a trematode. 1. Skin Diseases due to Parasitic Funcji. Favus (&quot;honeycomb ) is a common disease of the scalp (more rarely of the hairless parts of the skin) in children, primarily of scro fulous or ill-cared-for children, but apt to spread to others, especially in schools. The uncomplicated appearance is that of a number of yellowish circular cup-shaped crusts, grouped in patches like a piece of honeycomb, each about the size of a split pea, with a hair pro jecting in the centre. This was the first disease in which a fungus was discovered by Schonlein in 1839 ; the discovery was published in a brief note of twenty lines in Mailer s Archiv for that year (p. 82), the fungus having been subsequently named by Kemak Achorion Schonleinii after its discoverer. The achorion consists of slender mycelial threads matted together, bearing oval nucleated, gonidia either free or jointed. The spores would appear to enter through the unbroken cutaneous surface, and to germinate mostly in and around the hair-follicle and sometimes in the shaft of the hair. Favus is commonest among the poorer Jews of Russia, Poland, Hungary, Galicia, and the East, and among the same class of Mohammedans in Turkey, Asia Minor, Syria, Persia, Egypt, Algiers, &c. It is not rare in the southern departments of France, in some parts of Italy, and in Scotland. The treatment of favus is difficult and disappointing. The first requisite is good feeding; meanwhile the crusts are to be removed by poulticing, the hair being cut short. The next thing is to destroy the fungus, to which cud a lotion of sulphurous acid (one part to three or four of water) may be applied repeatedly by means of lint, and the scalp kept covered by an oil-silk cap. To prevent the return of the fungus, various agents may be rubbed in, such as cod- liver oil, oil of cade, or an ointment of iodine or of pitch, the oil-silk cap being worn continuously. It has often been found of advantage to pull out all the broken stumps of hairs with a tweezers (ste Bennett s Prin. and Prad. of Mcd., 5th ed., Edin., 1868, p. 847). Ringworm, or Tinea Tonsurans, a much more common disease of the scalp (especially within the tropics), consists of biild patches, usually round, and varying in diameter from half an inch up to several inches, the surface showing the broken stumps of hairs and a fine whitish powdering of desquamated epidermic scales. In scrofulous subjects matter is sometimes produced, which forms crusts or glues the hairs together or otherwise obscures the characteristic appearance. The disease is due to a fungus, Tri- chophyton tonsurans, which exists mostly in the form of innu merable spores (with hardly any mycelium), and is most abund ant within the substance of the hairs, especially at their roots. If a piece of the hair near the root be soaked for a time in dilute liquor potassre and pressed flat under a cover-glass, the microscope will show it to be occupied by long rows of minute oval spores, very uniform in size, and each bearing a nucleus. The treatment of ring worm is very much the same as the treatment of favus. The same fungus sometimes attacks the hairs of the beard, pro ducing a disease called &quot;sycosis. &quot; Sometimes it invades the hairless regions of skin, forming tinea circinata ;&quot; circular patches of skin disease, if they be sharply defined by a margin of papules or vesicles, may be suspected of depending on the tinea-fungus. Interesting vaiieties of tinea are found in some of the Pacific and East Indian islands. A less serious condition of the skin due to a fungus is Pttyriasis Hydro,&quot; Quart. Jour. Microfcop. &amp;lt;/., 1SS2; Soiby, &quot;On Ihe Cliromatologicul Relations of Spongilla fluviatilh&quot; Quart. Jour. Mitroteop. Sci., 1875; Geddes, &quot;Observations on the i hysiology and Histology of Conroluta Schultzii,&quot; Pro?. Roy. Soc. Lou-/., 1879, and &quot;On the Nature and Functions of the Yellow Cells of Radiolarians and CoMenteiates,&quot; Pmc. Roy. Soc. Edin., 1882; Haeckel, &quot; Amy- Uim in d. gelben Zellcn d. Radiolar,&quot; Jena Zeitsch., 1S70; Cieukouski, &quot;Ueber SchwiirmeibiUhniK bei Radiolar ,&quot; Archie. Mikr. Anat. 1871; R. Herfwig, Zur Jlisloloyie tier Radiolar..&quot; 1870 ; Per Organismus der Radiolar. . Venn Denkfchr., 1879; 0. and R. Hertwig, &quot;Die Actinien,&quot; Ji-na Zeilfc/ir., 187(1; O. Hertwig. Die Sijmbiofe, 1883; Brandt, &quot;Untersuchungcii an Iiadiolaiien,&quot; ifonatsb. Akact. fieri., 1881 ; Id., &quot;Ueber il. Zusammenlcben von TJiieren und Algen,&quot; Vtrhandl. d. phusiol. Gcf. zu Ilerl., 1881 ; Id., &quot; Ueber d. Morph. u. I hyMol. Beileutung d. Chlorophylls bei Thieren.&quot; Arch. f. Anat. u. J hysM., 1882, and Mittheil (I. Zoo/. Stat. , enpe/, 1883; Entz, &quot; Ueber d. Xatur. d. Chlorophyll-KCrperchen nicdercr Tiere,&quot; ISiol. Cenlratblatt, 18K2; Korotneff. &quot;On Myrtothela&quot; Soc. Xat. Hist. ,1/osl-. 1881; Moscley, Notes &amp;lt;&amp;gt;/ a Naturalist on the ;l Challenger,&quot; p. 2M.