Vice-President' s Address. 25 



diameters, with corresponding variety of skull shape, do not 

 impede or stop brain growth. It appears, therefore, that 

 brain growth and cranial ossification provide two sets of 

 conditions, which react upon each other in producing the 

 different forms of crania. 



No doubt the period at which parturition occurs in the 

 human subject is affected by the size of the foetal brain in 

 relation to the maternal pelvic diameters, but the difficulties 

 attendant upon human parturition are rather concomitants of 

 the erect attitude than results of the shape of the fcetal head, 

 which may be moulded in adaptation to any pelvic diameter. 

 The changes in the shape of the sacrum, together with the 

 increased strength and shortening of the sacro-sciatic liga- 

 ments necessitated by the erect attitude, must naturally 

 cause increased difficulty in parturition among civilised as 

 compared with primitive races, merely by reason of the 

 advanced evolution of the erect attitude. 



The frequence with which the skulls of civilised races 

 present an unobliterated suture between the two halves of 

 the frontal bone, constituting what is called a metopic skull, 

 as compared with the normal obliteration of this suture at a 

 comparatively early date, has led craniologists to regard this 

 condition as a variation which is tending to become typical. 



In this fragmentary summary of some of the anatomical 

 evidences in support of an evolutionary process which has 

 resulted in the marvellous mechanism we call Man, I have 

 given you examples of structural arrangements which are 

 most readily understood, on the assumption that they are 

 historical repetitions of bygone conditions which were prob- 

 ably at one time normal. I have also given you illustra- 

 tions of the introduction of new structural features, which 

 may, in their turn, become the normal type instead of the 

 occasional variation. 



The causes affecting and determining a process of evolution 

 are therefore quite clearly still at work, and, as in past ages, 

 so " in the ages to come," Man's body will continue to adapt 

 itself to his environment and his needs, by the " survival of 

 the fittest" in the great and increasing "struggle for exist- 

 ence." Nothing seems more certain than that the great 



