PHYSIOLOGY. 



arid in the propulsion of the child from 

 the uterus. 



The state of the mind considerably af. 

 fectsthe mode of respiration, although the 

 muscles of that function are so far inde- 

 pendent of the will, that they act without 

 any exertion of volition, and continue their 

 functions during sleep, when all the vo- 

 luntary powers are suspended. When 

 the lover, plunged in a soil reverie, fetches 

 a deep sigh, the physiologist observes a 

 strong and protracted inspiration, follow- 

 ed by a similar expiration ; crying and 

 sobbing, differ from sighing only in the 

 circumstance of the expiration being in- 

 terrupted, or divided into several distinct 

 periods. In gaping, which is attended 

 \vith a sense of weariness, there is a large 

 inspiration, accomplished in a gradual 

 manner, and by a kind of effort; the en- 

 trance of a great quantity of air is facili- 

 tated by opening the mouth wide : this 

 is followed by a complete gradual expi- 

 ration. Sneezing is a strong and violent 

 Expiration, and the noise accompanying it 

 is produced by the air passing out with 

 rapidity, and striking against the winding 

 parietes of the nasal fossae. The effort, 

 which is occasioned by the irritation of 

 the pituitary membrane, is a convulsive 

 motion of the muscles of respiration, and 

 particularly of the diaphragm. In cough- 

 ing, the expirations are shorter and more 

 frequent; the expelled air carries off the 

 mucus lodged in the trachea and bron- 

 ehise, and this discharge constitutes ex- 

 pectoration. Laughing is a short inspi- 

 ration, followed by several short and ra- 

 pid expirations. 



The alternate dilatation and contrac- 

 tion of the chest, proceed uninterruptedly 

 From the moment of birth to the end of 

 life, and in a healthy adult are repeated 

 about fourteen times in a minute, so that 

 each act of respiration corresponds pretty 

 nearly to five pulsations of the heart. For 

 an account of the changes which the blood 

 experiences in respiration, as well as those 

 which take place in the respired air, and 

 for the composition of the blood itself, see 

 RESPIRATION and BLOOD. 



The action of the lungs upon the blood 

 is so essential to the continuance of lite, 

 that its interruption very speedily causes 

 death. Yet, in these cases, absolute death 

 does not occur instantly, but the vital 

 processes, although suspended for a time, 

 may be renewed by a proper treatment ; 

 and hence arises the possibility of recover- 

 ing the apparently dead from drowning, 

 See. On the subject of sudden deaths, 

 Av.e may observe, that the organic func- 



tions may subsist after the animal areex- 

 tir.guisiH.-d, as in apoplexy, concussion, 

 &c The latter, however, never continue 

 after 'he former have ceased, as in great 

 haemorrhages, wounds of the heart, as- 

 phyxia, &c Hence the cessation of or- 

 ganic life is a sure indication of general 

 death, while that of animal life is a very 

 fallacious one. 



In explaining the effect which the ces- 

 sation of respiration produces, some havfe 

 stated, that the lungs, being no longer 

 distended by the air in inspiration, have 

 their vessels folded, and consequently me- 

 chanically unfit for the circulation of blood 

 through them Bichat, in his excellent 

 " Recherches sur la Vie et la Mort," has 

 fully disproved this statement, and has 

 shown, by incontrovertible experiments, 

 that neither the empty state of the lungs 

 in complete expiration, nor their distend- 

 ed condition in the most full inspiration, 

 produces any obstacle to the passage of 

 blood through the pulmonary vessels. 

 He proves, likewise, that when the ces- 

 sation of the chemical phenomena of the 

 lungs induces a cessation of the heart's 

 action, this does not happen in conse- 

 quence of the simple contact of black 

 blood with the internal surface of the left 

 ventricle ; but in consequence of this 

 blood, thus deprived of those principles 

 which are necessary for maintaining the 

 actions of parts penetrating the tissue of 

 the lieart, and coming into contact with its 

 fibres. The brain is affected in the same 

 way, in consequence of the cessation of 

 respiration ; and the arrival of venous 

 blood in this organ, causes an immediate 

 cessation of animal life, while the organic 

 still subsists. The same blood, too, accu- 

 mulated in every other structure, pro- 

 bably affects the whftle body with its mor- 

 tiferous qualities ; and consequently, a 

 mechanical inflation of the lungs with 

 pure air, is the most powerful method of 

 recovery that can be adopted in these 

 cases. 



The term asphyxia, signifying absence 

 of the pulse, is applied to every apparent 

 loss of vitality, produced by an external 

 cause that suspends respiration, as drown- 

 ing, strangling, disoxygenation of the air 

 we breathe, &c. The difference between 

 asphyxia and real death is, that in the 

 former state the principle of life may be 

 re-animated, while in the latter it is com- 

 pletely extinct. In those cases where it 

 arises from drowning, strangulation, and 

 some of the non-respirable gases, as car- 

 bonic acid ; the cessation of respiration is ' 

 the cause, and the treatment must be con- 



