ALKALOIDS, PTOMAINES, AND OTHER POISONS 499 



certain diminution has been observed, the imperfection of the available 

 methods of detection renders it doubtful whether the apparent decrease 

 is not merely due to the distribution of the substances in question over 

 the increasing volume of the growing plant *. 



Poisons are by no means essential products of metabolism ; thus in the 

 sweet almond the power of producing amygdalin has been entirely lost, 

 and Vogel 2 was unable to detect any quinine in chinchona plants grown 

 in European hot-houses. It is also possible for the hemlock often to 

 contain no conine in Scotland, for the production of alkaloids is markedly 

 dependent upon the cultural conditions 3 . Still more marked variations are 

 shown by pathogenic bacteria, which may exhibit all grades of virulence 

 according to whether the mode of treatment or culture is adapted to 

 diminish or increase their power of producing the specific poisonous substances 

 to which the pathogenic character of the bacterium in question is due 4 . 

 Alterations of this kind may be either temporary or permanent : thus 

 Bacillus antJiracis becomes permanently non-virulent after prolonged culture 

 at 42 C., but after a short exposure to 50 C. the virulence gradually 

 returns when the microbe is cultivated under normal conditions. Even the 

 permanently non-toxic forms may be rendered toxic by special treatment, 

 just as sweet almonds may occasionally become bitter again. The rapidly 

 reproducing micro-organisms are especially suitable for experiments of this 

 kind, and it may be found possible to obtain similar results with regard 

 to the production of enzymes or of other substances which are accessory 

 products of metabolism. 



Many poisonous substances may occur in widely different plants, and 

 the toxalbumins which occur in the seeds of Abriis precatorius and Ricinns 

 as well as in bacteria and in the sporophore of Anianita p/ialloides'", may 

 possibly be detected in many of the higher plants. Many bacteria pro- 

 duce their specific poisons only when fed with proteids, others, however, 

 also when no proteids are supplied, but nothing definite is known as to 

 the precise metabolic origin of poisonous substances in general. Poisons 

 are usually directly formed by the protoplast, but may also arise outside 

 the cell by the extracellular action of certain excreta, as, for example, 

 when poisons are formed by the peptic digestion of fibrin. Similarly after 

 the death of a cell which contains amygdalin, prussic acid may be liberated 



1 Heckel, Compt. rend., 1890, T. ex, p. 88. Cf. Clautriau, Ann. d. 1. Soc. Belg. d. Microscopic, 

 1894, T. xvin, p. 47. 



2 Vogel, Sitzungsb. d. -Munch. Akad., 1885, p. 6. 



3 Rochleder, Phytochemie, 1854, p. 344. Cf. Darwin, Variation of Plants and Animals under 

 Domestication, p. 314; Ludwig, Biol. d. Pflanzen, 1895, p. 222; Ad. Mayer, Versuchsst., 1891, 

 Bd. xxxvin, p. 453 (tobacco). On Agaricineae, cf. Bohm u. Kulz, Bot. Jahresb., 1885, P- 2 $- 



4 See Fliigge, 1. c., p. 299 ; Lafar, 1. c., p. 271 ; Burkmaster, Biol. Centralbl., 1895 , Bd. XV, p. 96. 



5 Neumeister, Physiol. Chemie, 1893, p. 228; O. Loe\v, Giftwirkungen, 1893. p. 76. 



K k 2 



