-208 THE HUMAN STERNUM. 



Emily. I am conscious of this peculiarity in the po- 

 sition of the head in some brute animals, such as the 

 horse, ox, sheep, &c., but I never observed any differ- 

 ence in this respect between the monkeys and man. 



Dr. B. Nevertheless, in the most perfect of the 

 ape kind those that most nearly resemble man in the 

 point of structure the space occupied by the base of the 

 skull in front of the spine, is twice that behind. 



Emily. After all, I do not clearly understand how 

 this arrangement indicates the erect position of man. 



Dr. B. Why, if he should attempt to go about on 

 all fours, the very few and small muscles of the neck 

 would be utterly incapable of supporting the head, and it 

 would inevitably fall forward. 



Emily. This seems satisfactory enough, but have 

 not some philosophers imagined that man in a state of 

 nature, as they call it, did actually go on all fours, but 

 had learnt to assume the erect position on account of its 

 greater convenience ? 



Dr. B. True, there have been men who would de- 

 grade our noble species to a level with the brutes, in its 

 origin, but few will be found, I suspect, at the present 

 day, to advocate their notions. The construction of the 

 human thorax, shows also, how thoroughly this reference 

 to the erect position has been kept constantly in view. 

 In all other animals, its greatest diameter is from be- 

 fore backwards, but in man alone, it is flattened anter- 

 iorly ; its greatest diameter being from side to side. 

 The tendency of this arrangement you will readily per- 

 ceive. 



Emily. If it extended to the front, rather than to 

 the sides, its tendency to fall forward would evidently be 

 greater, but the necessary room being obtained by ex- 

 tending it at the sides, the preponderance forward is 

 greatly diminished. Am I right ? 



Dr. B. Yes ; it likewise gives greater breadth to the 

 shoulders, and consequently more extensive motions to 

 the arms. The human breast-bone also is remarkably 



