March 23, 1905J 



NA TURE 



497 



leaf or other organ of a plant, bored its way in, or through 

 a stoma, and entered the tissues. Here it lived, as does a 

 plant in any other medium, at the expense of the substances 

 in the tissues, which it eventually kills. It then emerges 

 and develops its spore on the outside. 



Thus was founded the " germ theory " of disease. 



The lecturer here gave illustrations of the kinds of para- 

 sites referred to, and showed how the spotting of leaves is 

 brought about by various epiphytic and endophytic forms, 

 such as Oidium and Erysiphe, Phytophthora, Ustilaginese 

 and UredinecB, &:c., and directed attention to certain special 

 genera, such as Botrytis, Aspergillus, &c. 



That the ancients were acquainted with the phenomena 

 of rot in timber is attested by remarks of Theophrastus on 

 hollow trees and the decay of oak ; but it was not until about 

 1830 that any idea of connecting the phenomena with fungi 

 can be traced, and even then Theod. Hartig, who dis- 

 covered hyphjE in the rotten wood, thought they originated 

 from the wood-fibres themselves. Schacht, in 1850 and 18(53, 

 figured many instances of hyphae in wood, and showed that 

 the fungus fed on the starch, pierced the cell-walls, and in 

 some way induced their putrefaction ; and to these and 

 Willkomm's researches, in 1864, we may trace the origin of 

 our knowledge of fungi as the causes of decay in timber. 



.Meanwhile the palaeontologists also were bringing 

 forward examples of fungus-hyph.Te in fossil woods. 



But the real founder of this important subject was R. 

 Hartig, who in his works, 1874 and 187S, proved that not 

 only are there several kinds of wood-rots in different species 

 of trees, each induced by different forms of fungi, but that 

 the different woods show special markings, and break up 

 in peculiar manner for each case, so that particular kinds 

 of rot can be recognised by particular symptoms. Hartig, 

 moreover, showed how the fungi got into the tree, and that 

 these wound-fungi have special peculiarities. He traced 

 their hyphae into the vessels and wood-elements, showed how 

 they pierce the cell-walls, and, most important of all, proved 

 that they dissolve out from the wood-elements the lignified 

 constituents to which their fundamental physical properties 

 — as wood — are due, and either leave the delignified walls 

 soft and cellulose in character or dissolve them to a jelly. 



Here the lecturer showed illustrations of the mode of 

 action of dry rot, of Polyporus igiiiariiis, and of other wood- 

 destroying fungi, and referred to Czapek's recent discovery 

 of Hadromal, the probable uniform constituent of wood 

 hitherto vaguely known as Lignin. 



In another direction activity was turned to the fungi 

 which attack insects, and which are now known often to 

 become epidemic, to the great advantage of areas devastated 

 by locusts, cockchafers and other grubs, caterpillars, &c. 



It is a remarkable fact that whereas the diseases of plants 

 due to fungi are numbered by their thousands, only some 

 two hundred or so of animal maladies due to fungi proper 

 are known. Whether this is due to the more acid nature 

 of vegetable sap, to the high temperature of animal tissues, 

 or to the greater abundance of the anti-bodies in animals 

 cannot be decided. 



The lecturer gave illustrations of caterpillars with their 

 destroyers, Cordyceps. Isaria, &c., growing from their 

 mummified bodies, and referred to Torrubia's " Vegetable 

 Wasp " legend of 1749. He also showed photographs of the 

 " plant-worms " used in Chinese medicine, and rapidly 

 surveyed the work of Cesati, Pasteur, De Bary, Cohn, &c., 

 on Muscardine, Entomophthora, Empusa, Saprolegnia, and 

 other insect-killing fungi. 



But these entomophagous fungi are merely particular 

 cases of mycoses. Every group of animals from the Protozoa 

 and Infusoria upwards have their fungus parasites ; hyphae 

 penetrate the ceratin of sponges and the calcareous walls of 

 corals, and fishes and amphibia are by no means immune. 



Birds and mammals suffer particularly from certain 

 mycoses due to fungi which we have been in the habit of 

 regarding as harmless moulds, e.g. .Aspergillus, and even 

 man is sometimes in danger from such fungi. 



When, in 1869-70, Grohe and Block showed that small 

 doses of the spores of Penicillium and .Aspergillus are fatal 

 to kittens, their statements were emphatically disbelieved ; 

 but Grawitz confirmed them, and the body of evidence show- 

 ing that Aspergillus contains poisons toxic to birds and 

 higher animals can no longer be overlooked. Some of these 

 forms of aspergillosis are very serious diseases indeed. 



NO. 1847, VOL. 71] 



While the new era of mycology was stimulating observers 

 to new investigations into the life-histories of moulds, and 

 of the parasites of animals and plants, and into the aetiology 

 of the timber-destroying fungi, and so forth, on the one 

 hand, it was, on the other, gradually attracting to its 

 domain areas of investigation which had grown up inde- 

 pendently out of the past, and which the older thinkers 

 could never have dreamed of associating with fungi. 



A conspicuous example was the study of fermentation, 

 which, since Janssen in 1590 had brought forward a micro- 

 scope of several lenses, and Leeuwenhoek had applied an 

 improved form of it to the animalculae in putrefying liquids, 

 had undergone the initial stage of passage into the hands 

 of the naturalists. 



The lecturer then sketched in rapid outline the history of 

 the theory of fermentation, from the early days when the 

 lees or sediment (yeast) were known as the" Faeces Vint "-- 

 apparently owing to the shrewd suggestion of a Venetian 

 doctor, who, in 1762, said putrefactive and fermentation 

 processes are due to the vital activity of minute worms, the 

 excreta (faeces) of which induce the turbidity and mal-odour 

 of the liquid — to the days when the living plant-nature of 

 these " faeces " was gradually established by the work of 

 Astier, 1813, Desmaziferes, 1826, Ouevenne, 1838, and Per- 

 soon, and especially by Erxleben, 1S18, Kiitzing, 1834, 

 Cagniard Latour and Schwann, 1837. 



.At the same time, the sketch included an outline of the 

 first great controversies regarding abiogenesis or spontan- 

 eous generation, brought forward from its ancient strongholds 

 in the ignorance of the classical and mediaeval writers — e.g. 

 Pliny, Bock, Van Helmont — by Needham in 1745, and 

 confuted by Spallanzani, 1765-76, Schultze, 1836, Schroder 

 and Dusch, 1854; and to which the coup de grdce was given 

 by the work of Pasteur, 1862, Cohn, 1870-75, and Tyndall. 



Information derived from the brewing of quass, saki, 

 pulque, kava, toddy, koumiss, mead, metheglin, spruce 

 and other beers and wines by peoples all over the world has 

 only confirmed the ideas, of Pasteur especially, that all such 

 fermentations are due to the presence of fungi ; and although 

 the discussions as to the process itself being due to catalytic 

 actions and the communication of internal movements to the 

 molecules of sugar broken up, initiated by Stahl in 1697, and 

 revived in various forms by Liebig, 1839, and Naegeli, 1879, 

 culminating in Buchner's views on the discovery of zymase 

 in 1896-97, have modified the older forms of the vitalistic 

 theory of Cagniard Latour and Pasteur, they have not 

 dissociated fermentation from the life of the cell. 



The lecturer then passed to a survey of the enzymes, 

 those remarkable bodies which, though not themselves living, 

 are capable of breaking up organic substances apart from 

 the protoplasm of the cells which secrete them, and showed 

 that since the discovery of diastase in malt by Payen and 

 Persoz in 1833, of pepsin in gastric juice by Schwann in 

 1836, and of invertase in yeast by Berthelot in i860, 

 numerous other special enzymes have been isolated, and all 

 the principal forms of sugar-inverting, starch-saccharifying, 

 cellulose-dissolving, fat-splitting, proteid-converting, and 

 oxidising enzymes occur in the fungi. Bourquelot has 

 shown the presence of nine such enzymes in Polyporus sul- 

 phureus and of seven in Aspergillus alone. 



The presence of certain deadly poisons in putrefying fish, 

 flesh, &c., and the researches consequent on the increasing 

 knowledge of septic poisoning of wounds — with which Lister 

 dealt so practically at the time— led to researches which,_ in 

 the hands of Brieger, Sonnenschein, Armand Gautier, 

 Selmi, and others resulted in the isolation of more or less 

 specific bodies, such as sepsin, cadaverine, ptomaines, leuco- 

 maines, &c. In 1876 Neucki obtained an unusually pure 

 form, and the doctrine of ptomaine poisons may be regarded 

 as thereby established. 



For us, the point of interest here is that these poisons 

 proved to be analogous, if not identical as a class, with a 

 number of vegetable poisons, such as atropine, brucine, 

 nicotine, strychnine, or at any rate presented striking re- 

 semblances to them in their physiological actions. 



As close, or even closer, resemblances were found in the 

 poisons extracted from the fungi ; amanitin, bulbosin, cor- 

 nutin, sphacelotoxin, &c., all came under the same general 

 category. In 1880 Pasteur showed that fowl cholera could 

 be produced by means of the poison excreted by the bacilli, 

 from which the bacilli themselves had been removed; and 



