342 William E. Kellicott 



also of the dogfish. Observation of many of the lower vertebrates in 

 nature (Fulton, '01, '06) and in captivity, such as the giant salamander 

 and some reptiles, shows that these grow indeterminately; Agassiz's, '57, 

 observations i;pon Chrysemys are typical. As a recent example of the 

 failure to make this distinction we might mention the work of Eobertson 

 '08, who has devised certain formulae for the description of growth and 

 has brought out the very suggestive fact that the growth curve of an 

 organism or organ or tissue is similar to that given by an autocatalytic 

 reaction. These formulae hold good upon the assumption that the organ- 

 ism or organ has a definite period of growth at the end of which increase 

 in size ceases. This is true for the higher vertebrates, but for all the 

 indeterminately growing forms we can not determine any such "final 

 weight" of the body or organ upon which to base a formula. We could 

 not assume the maximum discovered size as the "final weight" because 

 this is subject to such extreme variation; in the dogfish, including both 

 sexes, we might find the "final weight" anywhere from 2000 to 8000 

 grams and even higher. 



We have already suggested, since the muscles, supporting tissues and 

 skin increase relatively much more rapidly than the other parts and 

 since this relation continues through life, that a time must come at which 

 the brain and metabolizing organs become incompetent as physiological 

 elements in the organism and death must result. As showing that this 

 relation is not one of mere bulk alone, Ave might recall some of the 

 observations of Hardesty, '05, on the frog. Here the number of spinal 

 ganglion cells as well as the number of dorsal and ventral root fibers 

 increases throughout growth, but inspection of his data shows that this 

 increase is at a constantly diminishing rate so that the relative number 

 of ganglion cells is constantly decreasing. Thus in a frog of 7.0 grams 

 there are in the ganglia of the V, VII, IX nerves respectively 103, 77.8, 

 549 cells per gram of body weight, while in a frog of 63.4 grams the 

 corresponding numbers are 15.9, 18.1, 72.7, although the actual numbers 

 of cells contained have increased 41, 111, 20 per cent respectively. In 

 general the same is true for the number of fibers in the dorsal and 

 ventral roots. Hardesty points out that this increase in number of 

 ganglion cells is opposed to the tradition regarding the nerve cells of 

 vertebrates which is supported by Hatai, '02, who found in the rat no 

 increase in the number of ganglion cells during growth, but only increase 

 in the number of mature fibers. 



Beddard, '03, found in a giant salamander which died in the Zoologi- 

 cal Society's Gardens that the only visible cause of death was the small 



