48 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



hyperplasia and hypoplasia of the gland. Other patho- 

 logical tissues have been investigated by various authors, 

 but the results, apparently, have not been so definite. 



Experimental modifications of mitochondria have been 

 induced by various methods. Ciaccio in 1913 observed the 

 changes in the mitochondria of various tissues after phos- 

 phorus poisoning. The following year Mayer, Ratherj" 

 and Schaeffer investigated the effects of phosphorus poison- 

 ing on the mitochondria of the liver. They found pleo- 

 morphic modifications of the mitochondria as well as 

 destruction of these bodies. In 1916, W. J. M. Scott 

 investigated the effects of experimental phosphorous poison- 

 ing on the mitochondria of the pancreas in white mice. 

 Scott's results are particularly interesting when compared 

 with the behavior of mitochondria in culture media. He 

 found that the first change observable in the mitochondria 

 in mild poisoning is a loss of the bleb-hke swellings normally 

 present in pancreas mitochondria and a thickening and 

 shortening of these bodies. When the poisoning is carried 

 further, the mitochondria clump together like agglutinated 

 bacilh. In more severe cases the agglutinated forms appear 

 to fuse and completely lose their identity. In some of the 

 stages described by Scott, he found globular bodies which 

 appeared to contain a vacuole. In some instances, only a 

 peripheral ring stained with the dye used, the center appear- 

 ing clear. These forms, apparently, are identical with the 

 pleomorphic mitochondria, to w^hich I have previously 

 referred as ''ring forms." 



Nicholson, in 1924, used various means to modify experi- 

 mentally the mitochondria of the thyroid. The blood 

 supply to the gland was interfered with in one set of experi- 

 ments. After three days the mitochondria which, nor- 

 mally, are filamentous were shorter and more granular. 

 After the tenth day they had become spherules. 



In another set of experiments, about three-fourths of the 



