kands couid not guard. She has given more thickness to the back part 

 of the skull; the skin which covers the neck and back, is much denser 

 than that which covers the fore part of the body. The scapula, in addi- 

 tion to the ribs, protects the posterior part of the chest. The spinal 

 column lies along the whole length of the back ; the bones of the pelvis 

 have their whole breadth turned backward. 



Falls are the more serious, as they occur in a more perfect state w of 

 extension of the articulations; the falls of a child whose limbs are in an 

 fiabitual state of flexion, are much less dangerous than those of a strong 

 and powerful adult, whose body falls in one piece, if I may be allowed 

 that expression. The falls which skaiters meet with, on the ice, are often 

 fatal from fracture of the skull, which, placed at the extremity of a long 

 lever formed by the whole body, whose articulations are on the stretch, 

 strikes the slippery and solid ice, with a momentum increased by the 

 quickness of the fall. 



We have already seen, that wading fowls remain a long while standing, 

 without effort, by means of a peculiar contrivance in the articulation ot' 

 the tibia to the thigh bone, but all other birds are obliged to employ mus- 

 cular action when standing, except during sleep. The greater part, it is 

 well known, roost on a branch which they grasp firmly with their claws. 

 Now, this constriction, by which they cling to their support, is a neces- 

 sary result of the manner in which the tendons of the flexors of their feet 

 descend along their legs. Tnese tendons pass behind the articulation 

 of the heel; a muscle which arises from the pubis joins them, as it passes 

 in front of the knee, so that the bird has but to give way \p his weight, 

 and the joints, becoming salient on the side along which the tendons run, 

 stretch and pull them, and make them act upon the feet, so as to draw in 

 the claws to clasp tightly the braneh on which he is perched. Borelli 

 was the first who understood distinctly and explained satisfactorily this 

 phenomenon*. 



CLXXXV. Although standing on both feet is most natural to man, he 

 is able to stand on one ; but the posture is fatiguing, from the forced in- 

 clination of the body to the side of the leg which supports him, and the 

 effort of contraction required to keep up this lateral inflexion. The dif- 

 ficulty increases, if, instead of resting on the entire soal, we choose to 

 stand on the heel or on the toe: the base of support is then so small, that 

 no effort is sufficient to keep the centre of gravity, long together, in the 

 requisite situation. 



As to the degree of separation of the feet, which gives the firmest pos- 

 sible stand, it depends upon their length. When they inclose a perfect 

 square, that is, when taking their length at nine inches, each side of the 

 quadrilateral figure is of that measure, the stand is the firmest that can 

 be conceived. Nevertheless, we are far from keeping or taking this pos- 

 ture to prevent falls. The wrestler who wants to throw his antagonist, 

 strides much more; but then, he loses on one side what he gains on ano- 

 ther ; and if he stride thirty-six inches, on the transversal line, it will 

 need much greater force to overthrow him on that side ; but it will take 

 much less to throw him forwards, or on his back. Wherefore, one 

 of the great principles of this gymnastic art, is to bring back the feet 



T)e motu dnimaUum, Prop. 150. Qn&rimr qitare aves stando, ranus arborum compre. 

 hemis, qui-esrnnt et dormiunt absquc ruina. Tab. II. fig. 7- 



