Chronological Changes in Placental Function 125 



ages, and there is evidence that its "efficiency", certainly for 

 some functions when considered in relation to foetal growth, 

 is increased in its old age; in fact, it might be said to be 

 abruptly expelled in the prime of life. 



REFERENCES 



Adair, F., and Thelander, H. (1925). Amer. J. Obstet. Gynec, 10, 172. 



Barron, D. H. (1951). Yale J. Biol. Med., 24, 169. 



Boyd, E. M. (1935). Biochem. J., 29, 985. 



Cooper, K. E., Greenfield, A. D. M., and Huggett, A. St. G. (1949). 



J. Phijsiol, 108, 160. 

 Elliott, R. H., Hall, F. G., and Huggett, A. St. G. (1934). J. 



Physiol., 82, 160. 

 Gellhorn, A., and Flexner, L. B. (1942). Amer. J. Physiol., 136, 750. 

 Hitchcock, M. W. S. (1949). J. Physiol, 108, 117. 

 Huggett, A. St. G., and Pritchard, J. J. (1945). Proc. R. Soc. Med., 



38, 261. 

 Huggett, A. St. G., and Widdas, W. F. (1949). J. Physiol, 110, 386. 

 Lochhead, J., and Cramer, W. (1908). Proc. roy. Soc. B, 80, 263. 

 Pritchard, J. J., and Huggett, A. St. G. (1947). J. Anal, Lond., 81, 



212. 

 Rodolfo, A. (1934). J. exp. ZooL, 68, 215. 



DISCUSSION 



Amoroso: It is evident that Professor Huggett does not feel inclined 

 to accept Lansing's definition of the ageing process. As I understand it 

 from what Professor Wislocki has said, Lansing considered the absence 

 of the powers of reconstruction in an ageing tissue to be an important 

 criterion of sensescence. 



Dawes: I would like to say how much I enjoyed Prof. Huggett's 

 exposition of the physiology of the placenta. I think that in any dis- 

 cussion of measurement of its efficiency, its functional efficiency should 

 be the overriding consideration. There is one rather odd finding that 

 I should like to comment on. Mr. Parry has been measuring the weights 

 of the placentomes in sheep and finds that, after the 120th day, the 

 total weight of the placentomes of a particular variety of sheep falls 

 very considerably from about 600 g. /foetus to 200-300 g. at term. 

 Whether this is a species difference, I do not know; it is just one more 

 of the many facts that are necessary to assess efficiency. 



Another point ; I was much impressed by the work of Cooper and 

 associates (Cooper, K. E., Greenfield, A. D. M. and Huggett, A. St. G. 

 (1949) J. Physiol, 108, 160) in measuring placental flow, which is tech- 

 nically difficult. They showed that flow through the foetal side of the 



