576 THE POPULAR SCIENCE MONTHLY. 



and brownish, next the wall of the bag, but thinner and more trans- 

 parent toward the centre (Fig. 8). This jelly (a) is called proto- 

 plasm, and the thin space (b) in the centre is an air-cell or vacuole 

 (Fig. 9). If you color the yeast-cells, you can see the different parts 

 much better. A drop of magenta will pass right through the sac 

 without staining it at all. The cell-jelly, or protoplasm, will be quite 

 red, and the vacuole will not be colored, though it may look pinkish, 

 because you see it through a layer of the protoplasm (Figs. 10, 11). 

 Now, if the cell were all made of the same material, it would probably 

 all be colored by the magenta. 



These cells are called torulze a single one is a torula. The word 

 means a little knobby swelling. You will soon see how it comes to 



Fig. 10. Jelly stained, and the Fig. 11. Broken Cell. 



Sac clear. Sac clear, Jelly stained. 



have this name. If you have followed me carefully, better still it you 

 have seen it all for yourselves under the microscope, you know that 

 the torula? are alive, and that they grow. Every thing that grows 

 must have food. Now, whence does the torula get its food ? From 

 the liquid in which it floats. What is this liquid ? The greater part 

 is water, but if you sow yeast in pure water it will hardly grow at 

 all ; but if you put in ever so little sugar, it will froth and bubble con- 

 siderably. If besides the sugar you give it the least bit of ammonia, 

 magnesia, lime, and potash, 1 it will thrive splendidly. The torula 

 takes in this food, and churns it up into that " elixir of life " or pro- 

 tein, woody cells or cellulose, and fat. Then, if you watch carefully, 

 you will see a whole lot of little buds coming out around the edges 

 of the wall (Fig. 12) ; hence the torula is really a little knobby swell- 

 ing. Some of the buds have other buds at their edges ; all these buds 

 are the little baby-torulas. By-and-by they break away from the old 

 mother-torula, but they always pay visits back and forth, and some- 

 times build their houses right next the parental roof in clusters (Fig. 

 13); at other times they build in long rows, like a chain or a string 

 of beads (Fig. 14). Of this you may be sure, every torula has a 

 mother. People have been trying to prove for two hundred years or 

 more that these little specks of life can make themselves. Some time 



1 pasteue's fluid. 



Parts. Parts. 



Potassium phosphate 20 Cane-sugar 1,500 



Calcium phosphate 2 Water 8,3*76 



Magnesium sulphate 2 



Ammonium tartrate 100 10,000 



