354 



increases with the length of the lever which they represent. So that, no 

 where is it greater than at the anterior extremity terminating in the 

 sternum. Thus, lying on the back has the double advantage of not con- 

 straining any of the muscles of inspiration, and of not opposing the mo- 

 tion of the ribs, except at that part where these bones have the least play: 

 lying on the back is one of the characteristic symptoms of putrid or ady- 

 namic fever, of scurvy, and of all the diseases of which debility of the 

 contractile parts forms the principal characteristic. After the fatigue 

 of a long march, or of any other continued exertion, we take this position 

 in lying, and change it, only when sleep has sufficiently replaced the loss 

 of contractility. 



Lying on the belly has effects directly the reverse. The expansion of 

 the chest is hindered, exactly where the bony structure is formed for the 

 greatest play of motion : the abdominal viscera are besides pushed up on 

 the diaphragm, of which they resist the depression, and the posture is 

 accordingly unusual. The continuance of it during sleep is possible only 

 to the robust 5 others, even when they do fall asleep in this posture, soon 

 awake from troubled and distressing dreams, under the agony known by 

 the name of the night-mare. We sometimes seek this posture to constrain 

 respiration, and so abate inward excitation, in the ardour, for instance, 

 of a febrile paroxysm. 



The different postures of lying having reference to the degrees of fa- 

 cility of respiration, very young children, and persons advanced in years, 

 prefer lying on the back, this posture being, as was already observed, 

 the most favourable to the motions of respiration. Respiration, like all 

 the other functions of the animal economy* with the exception of the 

 circulation and of the phenomena which immediately depend on it, re- 

 quires a kind of cultivation : it is but feebly performed at an early period 

 of life. It is only after a certain number of years, and when the muscles 

 of respiration, at first small and weak, acquire strength from the very 

 circumstance of being called into frequent action, that the chest dilates 

 'with facility, and that the lungs enjoy the full exercise of their faculties. 

 Until that period the enlargement of the chest and the dilatation of the 

 lungs took place, in an imperfect manner, the child was unable, even by 

 spitting, to free itself of the mucus with which its bronchias are apt to 

 get filled, and which render the pulmonary catarrh, called the hooping 

 cough, so dangerous at an- early period of life. In like manner, in an 

 old man, the muscles, debilitated, and returned to t,he relative weakness 

 of infancy, in vain strive to clear the air ceils of the mucus with which 

 they become obstructed in the suffocating catarrh. The mechanical 

 process of respiration is, therefore, equally difficult in the child, from 

 the weakness of the muscles which have remained in a long continued 

 state of inactivity; in the old man, from the debility of the same organs 

 and from the induration of the cartilages. Thus, at those two distant 

 periods of life, it is most natural to lie on one's back, but there is a suffi- 

 ciently remarkable difference in that respect, and which may now be in- 

 quired into. 



In the foregoing observations, I have always spoken of the human body 

 as stretched on a perfectly horizontal plane. It is seldom, however, that 

 \ve rest on such a surface,; almost every one, and especially persons ad- 

 vanced in life, require that the plane should be inclined, and that the 

 head should be raised to a certain degree, else the brain would become 

 affected with a fatal congestion of blood. Children, on the other hand, 



