28 THE CELL 



From time to time they wandered about the cage, raised their heads and occa- 

 sionally gasped. At eight o'clock they had become still more quiet and were 

 visibly very much exhausted, but on pricking them with a wire they still showed 

 indubitable signs of physiological integrity. On the following morning at nine 

 the frogs lay quite motionless. Even the most vigorous stimulus failed to pro- 

 duce any trace of reaction and there were no signs of respiratory movements. 

 At ten after a duration of seventeen hours the confinement was terminated and 

 oxygen was admitted. When after two hours' exposure to the atmospheric air, 

 and after repeated inflation of the lungs there was no sign of returning life, 

 Pfliiger opened the body cavity of one frog and found the heart still beating 

 with great energy and the arteries full of remarkably bright red blood. In spite 

 of this there were no muscular movements for five or six hours. Reflex irrita- 

 bility gradually returned, and spontaneous respiratory movements; but coordi- 

 nated movements such as are mediated only by the higher nerve centers did not 

 reappear at all. 



3. Finally, certain organisms of the lowest order, especially some of the 

 Bacteria, can maintain life permanently only in the absence of oxygen (anaero- 

 bic Bacteria, Pasteur). The yeast cell furnishes us some information concern- 

 ing the way in which the energy necessary for the functions of these organisms 

 is liberated. This organism can maintain life for a long time without air 

 and can develop considerable activity which displays itself notably in the 

 alcoholic fermentation of sugar i.e., by splitting grape sugar into 2(C0 2 ) 

 and 2(C 2 H 6 0). Since now the calorific energy of the alcohol formed is less 

 than that of the sugar destroyed, a certain quantity of energy is developed 

 and is placed at the disposal of the yeast plant (Hermann, Kiihne). 



In the dissimilatory processes of the cell the nutrient substances at its 

 disposal are gradually consumed, and if no supply from outside is kept up 

 the cell must of course die of hunger. 



The changes appearing in the cell body when it is deprived of nourishment 

 have been closely followed by Wallengren on the ciliate infusor Paramoecium. 

 During the first days of starvation all the food vacuoles and food masses dis- 

 appear. Thereupon the small granules present in the protoplasm are consumed, 

 and the endoplasm consequently decreases in quantity. At the end of this 

 period the living substance of the endoplasm is itself probably consumed in 

 part. In spite of the more or less profound changes in the form of the body 

 thereby produced, the ectoplasm, the contractile vacuoles and the cilia are still 

 not influenced in any noticeable way. During this period the activity of the 

 last-named 'structures is maintained by material supplied by the endoplasm. With 

 further inanition the endoplasm becomes much vacuolated, the ectoplasm, as 

 well as a large number of the cilia become more and more absorbed, and the 

 macronucleus is finally attacked, while the micronucleus remains comparatively 

 untouched. At last the point is reached where everything which the cell body 

 can furnish as nutrient material is consumed, the living substance remaining 

 is itself exhausted, and the cell, fallen into granular disintegration, perishes. 



C. Temperature. Since temperature exercises a very profound influence 

 on the various activities ' of cells, it will be appropriate to consider it in this 

 preliminary survey. We may safely aSsert that for every cell there is a definite 

 temperature which is most favorable to its life processes. The cell perishes 

 if the temperature passes beyond certain limits, although these limits differ 



