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at a greater distance from the centre of their motion, at an angle less 

 acute, and which increases in size, as the limbs bend. The union of 

 these causes gives to the limbs their superior power, and the greater 

 range of motion in these muscles, is a consequence of the arrangement 

 of the articulating surfaces, which almost all incline towards the side of 

 flexion. 



This preponderance of the flexor muscles, varies according to the dif- 

 ferent periods of life ; in the foetus, the parts are all bent very consider- 

 ably; this convolution of the young animal may be perceived from the 

 earliest period of gestation, when the embryo, of the size of a French 

 bean, and suspended by the umbilical cord, floats in the midst of the liquor 

 amnii, in a cavity of which it is more and more confined, as it approaches 

 to the period of its birth. This excessive flexion of the parts, which was 

 required to enable the produce of conception to accomodate itself to the 

 elliptical shape of the uterus, concurs in giving to the muscles which pro- 

 duce it, the superiority which they retain during the remainder of their 

 life. The new-born child preserves, in a very remarkable manner, the 

 habits of gestation ; but, in proportion as it grows, it straightens its body, 

 and, by frequent attempts to stretch itself, shows that a just proportion is 

 about to take place between the muscular powers. When the child be- 

 comes capable of standing erect, abandoned to its own powers, all its parts 

 are in a state of semi flexion, it staggers and is unsteady on its feet. To- 

 wards the middle of life, the preponderance of the flexors over the ex- 

 tensors, becomes less apparent; a man enjoys fully and completely his 

 power and locomotion; but, as he advances in years, this power forsakes 

 him; the extensor muscles gradually return to the state of comparative 

 debility of infancy, and become incapable of supporting the body, in a 

 fixed and permanent manner. 



CLXVI. The state of our limbs, during sleep, approaches to that of 

 the foetus, which according to Buffon, may be considered to be in a pro- 

 found slumber. The cessation of sleep is attended in man, as well as in 

 most animals, by frequent stretchings. We extend our limbs forcibly, 

 to give to the extensors, the tone which they require during the state 

 of waking*. Barthez accounts, in the same way, for the manner in 

 which the cock announces his waking, by crowing and flapping his 

 wings. 



It may happen in consequence of a morbid determination of the vital 

 principle, that our limbs may remain in a state of extension during sleep. 

 Hence Hippocrates recommends, that the state of the limbs be carefully 

 attended to, while the patient sleeps, for, as he observes, the farther that 

 condition is from the natural state, the greater the danger to be appre- 

 hended of the patient's life. In certain nervous diseases characterized 

 by a manifest aberration in the distribution of the vital power, a continued 

 state of extension must be considered a symptom highly dangerous ; I 

 have had several times occasion to observe, that in cases of wounds at- 

 tended with convulsions and tetanus, these alarming affections were an- 

 nounced by the permanent extension of the limbs during sleep, before a 



* Haller thinks, that these extensions are intended to relieve the uneasy sensations 

 occasioned by a long continued flexion, J\nnc quidem homines et animalia extendunt artus 

 quodiis fere con/lexis dormiant, etex eo pei^petuo situ, in musculis sensus incommodes oriatur, 

 quern extensione t ollunt, (phenomena ejcpergiscentium,} Elementa-physiologx, torn. V. p. 621, 



2 S 



