426 YEAST 



wood, and of an interior semifluid mass which contains a 

 substance, identical in its composition, in a broad sense, 

 with that which constitutes the flesh of animals. Subse- 

 quently, after the structure of the yeast plant had been 

 carefully observed, it was discovered that all plants, high and 

 low, are made up of separate bags or " cells," as they are 

 called ; these bags or cells having the composition of the pure 

 matter of wood ; having the same composition, broadly 

 speaking, as the sac of the yeast plant, and having in their 

 interior a more or less fluid substance containing a matter 

 of the same nature as the protein substance of the yeast 

 plant. And therefore this remarkable result came out 

 that however much a plant may differ from an animal, yet 

 that the essential constituent of the contents of these various 

 cells or sacs of which the plant is made up, the nitrogenous 

 protein matter, is the same in the animal as in the plant. 

 And not only was this gradually discovered, but it was 

 found that these semifluid contents of the plant cell had, 

 in many cases, a remarkable power of contractility quite 

 like that of the substance of animals. And about 24 or 25 

 years ago, namely, about the year 1846, to the best of my 

 recollection, a very eminent German botanist, Hugo Von 

 Mohl, conferred upon this substance which is found in the 

 interior of the plant cell, and which is identical with the 

 matter found in the inside of the yeast cell, and which again 

 contains an animal substance similar to that of which we 

 ourselves are made up he conferred upon this that title 

 of " protoplasm," which has brought other people a great 

 deal of trouble since I I beg particularly to say that, 

 because I lind many people suppose that I was the inventor 

 of that term, whereas it has been in existence for at least 

 twenty-five years. And then other observers, taking the 

 question up, came to this astonishing conclusion (working 

 from this basis of the yeast), that the differences between 

 animals and plants are not so much in the fundamental 

 substances which compose them, not in the protoplasm, 

 but in the manner in which the cells of which their bodies 

 are built up have become modified. There is a sense in 

 which it is true and the analogy was pointed out very many 

 years ago by some French botanists and chemists there is 

 a sense in which it is true that every plant is substantially 

 an enormous aggregation of bodies similar to yeast cells, each 

 having to a certain extent its own independent life. And 

 there is a sense in which it is also perfectly true although 



