52 BIOLOGY OF DEATH 



working out of its physico-chemical basis, we owe to Dr. 

 Jacques Loeb, of the Rockefeller Institute for Medical 

 Research. Artificial parthenogenesis may be induced, 

 as Guyer, Bataillon and Loeb have shown, even in so 

 highly organized a creature as the frog, and the animal 

 may grow to full size. The frogs shown in Figure 12, while 

 they present an appearance much the same as that of 

 any other frog of the same species, differ in the rather 

 fundamentally important respect that they had no father. 

 The role of a father was played in these cases by an 

 ordinary dissecting needle. Unfertilized eggs from a 

 virgin female were gently pricked with a sharply pointed 

 needle. This initiation of the process of development took 

 place March 16, 1916, in one case, and February 27, 1917, 

 in the other. The date of death was, in the first case, May 

 22, 1917, and in the other March 24, 1918. 



In the course of Loeb's studies of parthenogenesis in 

 lower marine invertebrates, he became interested in the 

 question of the death of the germ cells which had failed 

 to unite, or, having united, failed of appropriate envi- 

 ronmental conditions. His researches throw light on some 

 of the conditions of cellular death, and on that account 

 they may be reviewed briefly here. He found that the 

 unfertilized mature eggs of the sea-urchin die compara- 

 tively soon when deposited in sea-water. The same eggs, 

 however, live much longer, and will, if appropriate sur- 

 rounding conditions are provided, go on and develop an 

 adult organism, if they are caused to develop artificially 

 by chemical means or naturally by fertilization, Loeb 

 concluded from this that there are two processes going 

 on in the egg. He maintained, on the one hand, that there 

 are specific processes leading to death and disintegration; 

 and, on the other hand, processes which lead to cell divi- 



