SECT. 2] 



AND WEIGHT 



401 



The fall in the mitotic index ran closely parallel with the fall in the 

 percentage growth-rate of the organ, as determined by a special 

 series of weighings. The time taken by one mitosis was calculated 

 from these data by Olivo & Slavich : it turned out to be constant at 

 38 minutes. But the intermitotic period grew longer and longer, 

 indicating that the later growth consists less than the former of 

 proliferation and more of increase in size of the cells already formed. 



o 

 o\ 



( Males ] 



Z 5 811 17 23 29 3S3« 45 



75 80 105 120 135 150 165 180 185 210 dstye 241 



Fig- 43- 



For a long time Minot's way of looking at embryonic growth in par- 

 ticular and growth in general was universally adopted, e.g. by 

 Jenkinson, and even at the present time it is much used. But the 

 Minot curve is undoubtedly based on a fallacy, and it was not long 

 before a feeling that this was so began to arise. It was perhaps 

 intensified by the appearance of such estimates as that of 

 Muhlmann, who worked out the growth-rates in early stages of 



N E I . 26 



