ARTICULATION AND SUPPORT OF THE HEAD. 151 



magnitude of its parts, as well as to the ordinary attitude 

 of the body. The position and direction of the great occi- 

 pital foramen affords a criterion of these differences*. 

 The vertebral column being vertical in the human subject, 

 affords a solid support for the head, which is placed nearly 

 in equilibrio on its upper end. Hence the great occipital 

 hole and the articular condyles are found almost in the 

 centre of the basis cranii : and if the vertical line of the 

 trunk and neck were continued upwards, it would pass 

 through the top of the head : consequently the weight of the 

 latter is sustained almost entirely by the vertebral column. 

 The head would be in a state of perfect equilibrium on 

 the spine, in the erect attitude of our body, if the parts in 

 front of the column exactly counterbalanced those behind 

 it. This, however, is not the case f. The articular con- 

 dyles are manifestly nearer to the occipital tuberosity than 



* Daubenton sur la Difference du grand Trou Occipital dans V Homme 

 etdans les autres Animanx ; Mem. de VAcad. des Sciences^ 1764. 



+ I am unfortunate enough to differ with the author of the Physiological Lec- 

 tures in matters of fact, as much as in matters of opinion. To the following 

 assertion I can only oppose the circumstances mentioned in the text. " The 

 condyles are placed so exactly parallel in the centre of gravity^ that when we 

 sit upright, and go to sleep in that posture, the weight of the head has a ten- 

 dency to preponderate equally in every direction^ as we see in those who are 

 dozing in a carriage. Nay, their heads sometimes revolve in a circle, like 

 the head of harlequin on the stage." Lect. 3, The second expression 

 marked in italics cannot be taken literally ; because inequality is essential to 

 preponderance ; and an equal preponderance in every direction, if we dis- 

 regard the contradiction in terms, is just equivalent to no preponderance at 

 all. If the author means to assert that the weight behind exactly counter- 

 balances that in front of the occipito-atloidal articulation, the easy trial of 

 supporting a skull by the condyles will quickly shew whether such a repre- 

 sentation be correct or not. 



An analogous representation occurs in the same lecture respecting the dis- 

 tribution of weight in the trunk of the body. " We know that, in an upright 

 posture, the whole weight of the upper part of the body is so perfectly ba- 

 lanced on the base of the vertebral column, as to have an equal propensity to 

 preponderate in every direction." 



The weight of the head, of the thoracic and abdominal viscera, and the 

 ordinary position of the upper limbs, carry the centre of gravity in front of 

 the spine. The tendency of Ihc trunk to fall forwards is counteracted by 



