364 EXPERIMENTAL GIGANTISM 



Chambers, and by Nowikoff^^ that the division rate of Protozoa is not 

 increased if anterior lobe extract is added to the culture medium. 

 The same is true for the cells of warm blooded animals. In as yet 

 unpublished experiments Carrel found that in tissue cultures the 

 growth of the cells of warm blooded animals cannot be accelerated if 

 anterior lobe extract is added to the culture medium. ^"^ Our experi- 

 ments show, however, that the cells of the organism are still capable 

 of dividing at a time at which the organism as a whole has stopped to 

 grow. Apparently the cessation of growth of the organism as a whole 

 is not caused by a fundamental property of the cell to become incap- 

 able of growth, after growth has been going on for some time. This 

 corroborates the well known tissue culture experiments of Carrel 

 which would suggest that the cell protoplasm, if kept under proper 

 conditions, can go on dividing for indefinite periods. Since the hy- 

 pophysis-fed salamanders are still growing, it is impossible, at present, 

 to say how long the anterior lobe hormone can maintain, within the 

 organism as a whole, a condition permitting active growth of the cell. 

 But it is possible to say that the size of the individual is not an obstacle 

 to the further growth of an organism. It has frequently been claimed 

 that the size of every species is determined by the mechanics and 

 statics of the substances constituting the body of the organism. 

 Although these principles may be among the reasons why the organism 

 stops growing after it has attained a definite size, they cannot be the 

 only reason ; the occurrence of giants shows that at least a considerable 

 increase in the specific size of the species would result if the size of the 

 organism would be determined by the mechanic and static principles 

 alone. 



As pointed out above, the evidence that anterior lobe feeding can 

 produce gigantism in warm blooded animals is not yet sufficient. It 

 would be of great importance if it should be demonstrated that this 

 difference is due to the difference in the body temperature of amphib- 

 ians and warm blooded animals. Lenz^^ has recently called atten- 



15 Shumway, W., /. Exp. Zool., 1917, xxii, 529. Chambers, M. H., Biol. Bull., 

 1919, xxxvi, 82. NowikofiF, M., Arch. Protistenk., 1908, xi, 309. 



1^ I am indebted to Dr. Alexis Carrel for permission to quote these, as yet 

 unpublished, experiments, which were carried out in Dr. Carrel's laboratory. 



1^ Lenz, F., Munch. Med. Woch., 1919, Ixvi, 992. 



