79 



This does not imply that volutin-free yeast does not contain 

 nncleinic acid, as in working with very large quantities of yeast, 

 the nucleinic acid Will also be isolated from the nuclei, and will be 

 demonstrable in the filtrate. But it does imply that Torula monosa, 

 devoid of volutin, produces mucli less nucleinic acid than the normal 

 Torula. It is, therefore, quite justifiable to say that the volutin is 

 answerable for by far the greater part of the nucleinic acid, gene- 

 rally prepared from yeast. 



The fact that volutin-free cultures may be kept alive for months, 

 moreover that, when transplanted on phosphate-free media, a fresh 

 growth is developed, and lastly that on a phosphate-containing medium 

 volutin is formed again directly, shows conclusively tliat the i>resence of 

 this nucleinic acid compound is not essential to the vitality of these 

 cultures. This does not mean, however that the conditions of life 

 are not more favourable for the yeast-cells that contain volutin. On 

 the contrary, with them the growth is more rapid and more abundant, 

 the size of the cells is often larger. Nor is it to be expected, that 

 a substance, present in each yeast-cell to such a considerable amount, 

 has no function to perform in it. 



In how far the absence of phosphate in the nutrient medium — 

 aside from the volutin-production — is answeiable for the decrease 

 in the growth, could never be made out in these experiments. 

 Theoretically speaking the protoplasm of the yeast-cell may, also 

 apart from the volutin in consequence of the absence of this salt, 

 lack a stimulant agent that cannot be replaced by other salts. It 

 should not be forgotten, of course, that also in these phosphate- 

 free nutrient media traces of phosphorus were always demonstrable 

 microchemically, i. e. organic phosphorus-compounds that may be 

 borne off and assimilated by the cell to render the multiplication of 

 the nuclei possible. But for this the capacity of the yeast cells to 

 grow and to multiply would be out of the question, as has been 

 remarked above. The rare reports in the literature concerning a 

 growth on a medium entirely free from phosphorus, cannot bear 

 criticism as far as a careful analysis is concerned. 



It stands to reason that, alongside of the efforts to detect the 

 chemical nature of volutin, observers have always tried to establish 

 its significance in the life of the yeast-cell. The first observers who 

 studied these basophilic granules in moulds and bacteria naturally 

 inclined to believe them to be a reserve-material. When upon the 

 basis of Meyer's investigation it was surmised that volutin was 

 built up of nucleinic-acid compounds, it was natural that one should 

 look for some relation with the nucleus. But when nothing was 



