ATTITUDES STANDING. 439 



part of the lever that the power acts most forcibly; and it is there that 

 the pyramid is thicker, and that the spinous and transverse processes 

 are larger, and more horizontal. We can accordingly comprehend why 

 fatigue should be experienced in the loins and sacrum, when we have 

 been, for a long time, in the erect attitude. It need scarcely be said, 

 that the longer and more horizontal the spinous processes, the greater 

 will be the arm of the lever ; and the less the muscular force necessary 

 to produce a given effect. 



The weight of the whole of the upper part of the body is transmitted 

 to the pelvis; which, resting upon the thigh-bones as on pivots, repre- 

 sents a lever of the first kind, the fulcrum being in the ilio-femoral 

 articulations; the power and resistance situate before and behind. The 

 pelvis supports the weight of a part of the abdominal viscera; and the 

 sacrum that of the vertebral column, which, by reason of its shape, 

 transmits the weight equally to the ossa femorum, through the medium 

 of the ossa ilii. When the pelvis is, therefore, in equilibrium on the 

 heads of the thigh-bones, this is owing to 

 many causes. The abdominal viscera, Fi s- 191 - 



pressing upon the anterior part of the 

 pelvis, which is naturally inclined for- 

 wards, tend to depress the os pubis ; whilst 

 the vertebral column by its weight tends 

 to press down the sacrum. As the weight 

 of the latter is more considerable than 

 that of the former, muscles would seem 

 to be required to keep it in equilibrium, 



as Well as Others passing from the femur Lateral View of a Lumbar Vertebra. 



to be inserted into the os pubis, by the i.Body. 5. spmous process. 6. Trans- 

 contraction of which the excess of weight ISftit^SSSS^SST 

 of the vertebral column may be counter- 

 balanced. Such muscles do exist; but, as M. Magendie 1 remarks, they 

 are not the great agents in producing the equilibrium of the pelvis on the 

 thigh-bones ; for the pelvis, instead of having a tendency to be depressed 

 posteriorly, would appear to bear forwards, inasmuch as the muscles, 

 that resist the tendency which the spine itself has to bear forwards, 

 have their fixed point on the pelvis; and consequently exert a consider- 

 able effort to draw it upwards. The strong glutsei muscles, which form 

 the nates, and are inserted into the os femoris, are the great agents of 

 the equipoise; and as the hip-joint is nearer the pubis than it is to the 

 sacrum, these muscles act with a greater leverage. 



The thigh-bones transmit the weight of the trunk to the tibia ; and 

 here we see the advantage of the neck of the thigh-bone, which, as 

 represented in Fig. 192, B, joins the shaft at a considerable angle. 

 The trochanters I) and C are for muscular attachments; and are, of 

 course, advantageous to the muscles, which are inserted into them. 

 The cervix femoris directs the head of the bone, A, obliquely upwards 

 and inwards, so that, whilst it supports the vertical pressure of the 

 pelvis, it resists the separation of the ilia, which the pressure of the 

 sacrum, with its superincumbent weight, has a tendency to produce. 



1 Precis, &c., edit, cit., i. 296. 



