338 



RESPIRATION. 



ceived by other nerves than those distributed 

 in the lungs, is proved by the fact, which we 

 have witnessed, that a few distinct respiratory 

 movements may be observed in an animal 

 after its lungs have been removed. That 

 portions of the posterior roots of the spinal 

 nerves distributed in the external cutaneous 

 surface do act as excitors of respiration 

 under certain circumstances, is proved by 

 the effects of dashing cold water on the sur- 

 face of the body, especially on the face. It 

 is also probable that the circulation of venous 

 blood in the arteries of the medulla oblongata 

 may also cause the transmission of the motive 

 influence outwards to the respiratory muscles. 

 What are the excitations which lead to the 

 performance of the muscular movements of 

 expiration ? Do the same excitations that 

 occasion the muscular movements of inspira- 

 tion, operate in the production of the expira- 

 tion which immediately follows, so that they 

 are to be considered two stages of the one 

 and the same muscular action ? These are 

 questions which we are not prepared to 

 answer. When the functions of the medulla 

 oblongata are arrested, the motive influence 

 of volition cannot pass downwards from the 

 encephalon to the motor nerves that move 

 the chest in respiration ; and as all the ex- 

 cited or involuntary movements of respiration 

 of the same muscles must, for the reasons 

 already stated, instantly cease, immediate 

 death is the consequence. Destruction of a 

 portion of the spinal chord below the medulla 

 oblongata and above the origin of the phrenic 

 nerve will also produce the same result, for 

 though the excitations that lead to the per- 

 formance of the respiratory muscular move- 

 ments reach the medulla oblongata, the motive 

 influence cannot pass downwards to reach 

 the motor nerves distributed in the muscles 

 which act on the thorax. 



Frequency of the respiratory muscular move- 

 ments. The frequency of the respirations 

 varies in different individuals, and at different 

 ages, and is so much influenced by the condi- 

 tion of the body and the mind at the time, 

 even when the individual is in perfect health, 

 that it is a much more difficult matter to 

 determine their average frequency than may 

 at first be imagined. Quetelet* has con- 

 structed the following table on the frequency of 

 the respirations, at different ages, per minute, 

 from observations made on 300 individuals. 



Mr. Hutchinson * gives the following table 

 of the number of respirations per minute in 

 adults when in the sitting posture, in 1714 

 adults of the male sex, considered to be in a 

 state of health. 



* Sur 1'Homme et !e Developpement de ses Fa- 

 cultes, &c. torn. ii. p. 91. Bruxelles, 1836. 



From Mr. Hutchinson's table it would ap- 

 pear that the majority of male adults breathe 

 between 16 and 24* times per minute, and that 

 of these a great number make 20 respirations 

 per minute.-j- 



According to Prevost and Dumas J, the 

 ratio of the respirations to the pulsations of the 

 heart is as 1 to 4. According to Mr. Hutchin- 

 son , "the prevailing numbers run as four 

 beats of the heart to one respiration." Quetelet || 

 states, that " it does not appear that there is 



* Medico-Chirargical Transactions of London, 

 vol. xxix. p. 226. 1846. 



f The following results upon the frequency of the 

 respiration in a state of rest have been obtained by 

 others ; but as these were made upon their own per- 

 sons, they possess only the value of individual cases. 

 Dalton (Memoirs of the Literary and Philosophical 

 Society of Manchester, 2nd series, vol. ii. p. 26, 

 1813) found the number of his respirations to be 20 

 per minute ; Thomson (System of Chemistry, vol. iv. 

 p. 604, 1820), to be 19;" Sir H. Davy (Researches 

 chiefly concerning Nitrous Oxide and its Respira- 

 tion, p. 434, 1800), to be 26 or 27 ; Magendie" (Com- 

 pendium of Physiology, translated by Milligen, p. 

 390, 1831), to be 15 ; Dunglisson (Human Physio- 

 logy, vol. ii.), to be 16 ; and Allen and Pepys, on one 

 of themselves (Philos. Trans, of London for 1808), 

 to be 19. Menzies (Teutamen Physiol. Inaug. de Re- 

 spiratione, 1790), found them to be 14 in the minute 

 in the person on whom he experimented ; Vierordt 

 (Article " Respiration " in Wagner's Handworterbuch 

 der Physiologic, band ii. S. 834), in his own person, 

 found them on an average to be 11-^ when sitting, 

 and the mind disengaged; while their maximum 

 was 15, and their minimum 9. Dr. Guy (Hooper's 

 Vade-Mecum, edited by Dr. Guy) ascertained that 

 the respirations in his own person were 22 in a 

 minute while standing, 19 when sitting, and 13 

 when in the recumbent position. 



J Vide Burdach's Traite' de Physiologic, traduit 

 de rAllemand par Jourdan, torn. vii. p. 38. 1837. 



Journal of the Statistical Society of London, 

 vol. vii. p. 205. 



|| Op. cit. 



