CENTRE OF GRA VITY OF THE BOD Y. 



2 59 



method of finding the resultant of two or more parallel forces due to the 

 action of gravity on the centres of the limbs. 



One cannot read the work of these authors without the greatest admiration 

 for the care with which they have tried to settle an important problem, but it 

 is very doubtful if the mathematical calculations they have so rigorously 

 used can be applied with advantage to the case in point. To apply data 

 supplied from a corpse stretched upon its back, and subject before freezing to 

 the distortions of gravity acting in the front to back direction, to a somewhat 

 similar living man standing upright and subject to the distortion of gravity 

 acting in a vertical direction, is not a basis upon which we can hope, with 

 further work, however 

 careful and exact, to 

 obtain accurate results. 



As will presently 

 be shown, the deter- 

 mination of the position 

 of the centre of gravity 

 is of importance in 

 determining the posi- 

 tion of stable and un- 

 stable equilibrium. It 

 is here a matter of chief 

 interest to find out 

 whether the centre 

 plumbs in front or be- 

 hind the hip- and knee- 

 and ankle-joints ; to 

 determine, in fact, its 

 position in the sagittal 

 plane. This can easily 

 be determined by an 

 apparatus, contrived by 

 Dr. W. Sheen and my- 

 self, which is so simple 

 and easily manipulated 

 that it can be used by 



the physician as a FlG ' 145. -Apparatus for determining the centre of gravity. 

 ,. . r , . J T Above, the upper view of the box is shown. ab is 



Clinical instrument. It the board on which one foot rests, and which is tilted 



consists of a box, on 

 which the patient 

 stands upon both feet 

 (Fig. 145). The board 

 ab, on which one foot rests, is provided below with a steel runner like 

 that of a skate. The runner is supported at each end in a slot of metal. 

 The oblique front view of the apparatus is seen in the lower part of 

 Fig. 145. Below the runner is a strong steel rod, and by introducing 

 between the rod and the runner the bent lever, the runner can be 

 prised up at any point in its length. If the patient be standing with 

 his centre of gravity falling over the middle of the foot, and if we 

 prise up the runner in front, the front part . will be raised, the runner 

 resting on the lever and the back slot. On prising the runner behind 

 the ankle, the back part will be raised, for the centre is in front. On 

 prising the runner nearer and nearer the plumb-line through the centre 



by the lever I. Below is shown an oblique view of the 

 same, r is the rod on which the lever I rests, and x 

 the runner carrying the board ab. The indices at either 

 end of the board ab show which end is raised. 



