384 LECTURE XXIV. 



in the fluid by means of a needle point, etc. ; exactly in the same way as we expect, 

 in the artificial nourishment of a plant containing chlorophyll, that a plant of normal 

 size with numerous ripe seeds will develope from a seed. This the solution men- 

 tioned accomplishes ; though there still remain several things to be considered. 

 Naegeli says, that, theoretically considered, from a quantity of Yeast which cannot be 

 weighed 3-4 grams of new Yeast should be produced in the fluid described, whereas 

 in reality only i gram is produced. Nevertheless the result must not be under- 

 estimated, since a single Yeast-cell weighs only about ^lyshs-^^ of a milligram, 

 and thus in our solution there would arise from one or a few such cells some 2000 

 millions of new cells, and a corresponding increment of protoplasm and cellulose also 

 takes place. However, as already explained, I only introduce these numbers in order 

 to give a general idea of the matter to those unacquainted with such things. As a 

 matter of fact, Yeast-fungi, Bacteria and various Mould-fungi can flourish in very 

 different nutritive mixtures, if only a suitable carbon compound is present in addition 

 to the mineral matters mentioned. 



The most suitable carbonaceous food is always found by these Fungi in sugar 

 (glucose), and the best nitrogenous food in proteids and peptones. According to 

 Naegeli the nitrogen may be taken up simultaneously with the carbon also from 

 Acetamide, Methylamine, jGthylamine, Prophylamine, Asparagin and Leucin ; whereas 

 Oxamide and Urea can supply merely the nitrogen, but not the carbon. As sources 

 of nitrogen the Fungi can also make use of all ammonia-salts, and the Mould-fungi 

 and Bacteria even of nitrates. Free nitrogen, on the contrary, cannot be used for 

 the formation of protoplasm by the Fungi : exactly as is the case with the green 

 plants. In the same way Cyanogen compounds are unfitted for this purpose. 

 According to Naegeli, almost all carbon compounds are suitable for nutrition as 

 carbonaceous material, if they are soluble in water and not too poisonous; but 

 Cyanogen, Urea, Formic and Oxalic acids, and Oxamide are unsuitable for this 

 purpose. The best nutritive material in all cases is afforded by a mixture of peptone 

 and sugar. 



With regard to the production of plastic matters from the nutritive materials 

 taken up in the interior of the Fungus-cells, Naegeli has studied chiefly the 

 formation of fat (starch is as a rule not produced in the Fungi). There is not the 

 slightest doubt, after what I have stated previously, that fat is formed in ripening 

 seeds from carbo-hydrates, particularly starch, since this transformation takes place 

 in the" nearly ripe seed even when taken out of the fruit, where no other material 

 is available under the circumstances for the formation of fat. It results now, from 

 Naegeli's investigation, that in the lower Fungi also fat is formed from carbo-hydrates, 

 but also from albuminates and other nitrogenous carbon compounds. If Fungus- 

 cells are placed in pure water, fat is formed in them at the expense of their proteid 

 substance, since the protoplasm diminishes in quantity. This is very easily demon- 

 strated in the case of the Mould-fungi and Yeast. That albuminates and other 

 nitrogenous carbon compounds can yield material for the formation of fat may 

 be proved, according to Naegeli, when these substances (with the addition of the 

 necessary mineral matters) are exclusively employed for the nutrition. The Bacteria 

 (Schizomycetes) flourish in a solution of proteids, or still better of peptones formed 

 from proteids ; and the Mould-fungi grow in it when the solution contains a little 



