66 



Scientific Proceedings (63). 



males, the probability of the truth of this conclusion being 142 :i. x 

 The weight of the infants at birth increases regularly with the 

 length of the period of gestation. Plotting these weights as ordi- 

 nates with the corresponding periods of gestation as abscissae the 

 curve of growth thus obtained passes smoothly into the extra- 

 uterine curve of growth for South Australian infants, without 

 any indication of a slackening of growth such as occurs at or near 

 the junction of two growth-cycles. The intra-uterine growth of 

 infants, subsequent to implantation of the embryo, therefore 

 appears to be part of a single growth-cycle which culminates 

 towards the end of the first year of extra-uterine life. At or near 

 this period a junction of growth-cycles (slackening of growth) 

 occurs, and Macgregor 2 has shown that an unusual proportion of 

 infants are of subnormal weight at this period and that these 

 infants are selectively attacked by certain zymotic diseases. This 

 period therefore corresponds with the critical period detected by 

 Read in the intra-uterine growth of guinea-pigs. That it occurs 

 during intra-uterine growth in guinea-pigs and during extra-uterine 

 growth in human beings corresponds with the fact that guinea- 

 pigs are born in a relatively more adult condition of development 

 than man. 



44 (976) 



The post-natal loss of weight in infants and the compensatory 

 overgrowth which succeeds it. (PreUminary Communication.) 



By T. Brailsford Robertson. 



[From the Rudolph Spreckels Physiological Laboratory of the 

 University of California.] 



As stated in the preceding communication, it is possible, by 

 plotting the weights of infants born somewhat before the expiry 

 of the mean term of gestation against the length of the period of 

 gestation, to obtain a curve of intra-uterine growth which con- 

 tinues without any break or any period of loss of weight into the 



1 For the method of computing this probability cf. C. B. Davenport, "Statistical 

 Methods," 2d ed., New York, 1904, p. 14. 



2 A. S. Macgregor "Physique of Glasgow Children," Royal Philosophical Society 

 of Glasgow Proceedings, April 21, 1909. 



