THE PRESENT POSITION OF CELL-THEORY. 237 



not matter for present purposes. It is sufficient to know 

 that two substances, cytoplasm and nuclein, must be brought 

 together or life cannot exist, and that it does exist in 

 organisms in which these substances, and these only, can be 

 detected, viz., in Bacteria. This statement may appear some- 

 what hazardous, seeing that the presence of a nucleus is 

 denied in several living beings, in bacteria, for instance, and 

 in yeast. A nucleus in the sense of a centralised body is 

 certainly absent in these and in many other forms, but 

 Biitschli has demonstrated the presence of nuclein in 

 Oscillaria in Bacterium lineola. As for Saccharomyces it 

 undoubtedly contains nuclein, for Raum has prepared it 

 from yeast cells, and the most recent observer, Macallum, 1 

 is of the opinion that the nuclein is distributed through the 

 cytoplasm but also aggregated in the so-called granules of 

 Raum. 



The statement therefore can scarcely be called hazardous, 

 and it is really warranted by the facts at our disposal, for 

 the more carefully that researches are made, and the more 

 delicate the methods of investigations employed, the more 

 is the presence of nuclein demonstrated where it was not 

 previously supposed to exist. 



Macallum's paper, by the way, is of great interest, for he 

 shows that nuclein is essentially the iron-holding substance 

 in cells. Knowing as we do the close connection there is 

 between the presence of iron and the due performance of 

 the vital processes, this observation opens up a fruitful 

 source of inquiry as to the dependence of life on chemical 

 processes. 



Throughout this argument I have tried to stick to the 

 rule of drawing legitimate inferences from observed facts 

 without wandering into the obscure regions of hypothesis. 

 If I have been successful and have fairly stated the facts, 

 and have drawn legitimate inferences, the conclusion which 

 I come to must be admitted to be of considerable weight. 



1 A. B. Macallum, "On the distribution of Assimilated Iron Com- 

 pounds, other than Haemoglobin and Haematins, in Animal and Vegetable 

 Cells," Quart. Jour. Mir. Sri., vol. xxxviii., pp. 175-274, 1895. 



