374 OF RESPIRATION. 



The average numerical proportion of the respiratory movements to the pul- 

 sations of the heart, is about 1 : 5, 1 : 4, or 1 : 4 ; and when this proportion 

 is widely departed from, there is reason to suspect some obstruction to the 

 aeration of the. blood, or some disorder of the nervous system. 1 Thus in 

 Pneumonia, in which a greater or less amount of the lung is unfit for its 

 office, the number of respirations increases in a more rapid proportion than 

 the acceleration of the pulse; so that the ratio becomes as 1 to 3, or even 1 

 to 2, in accordance with the degree of engorgement. 2 In Hysterical patients, 

 however, a similar increase, or even a greater one, may take place without 

 any serious cause; thus Dr. Elliotsou 3 mentions a case in which the respira- 

 tory movements of a young female, through a nervous affection, were 98 or 

 even 106, whilst the pulse was 104. On the other hand, the respiration in 

 certain typhoid conditions and in narcotic poisoning becomes abnormally 

 slow, owing to the torpid condition of the nervous centres, the proportion 

 being 1 to 6, or even 1 to 8 ; and in such cases the lungs not unfrequeutly 

 become oedematous, from a cause hereafter to be mentioned ( 303). M. 

 Marey 4 believes it may be shown that the frequency of the respiratory acts 

 are, as in the analogous case of the heart, almost always diminished whilst 

 they are at the same time rendered deeper by the existence of any obstacle 

 to their due performance ; so that there is an evident attempt made to effect 

 within certain limits, the introduction of the same quantity of air into the 

 lungs in a given time ; and in an ingenious instrument he has devised, where, 

 by the reversal of a valve, difficulty of breathing may be induced either 

 during inspiration or expiration, he has observed that that act is prolonged 

 in which the dyspnoea is made to occur. 



293. We have now to inquire into the mode in which the Muscular move- 

 ments of respiration are kept up by nervous power. There can be no doubt 

 that these movements, though partly under the control of the Will, are 

 essentially "automatic" in their nature. Their chief centres consist of two 

 ganglia placed on either side of the point of the Calamus Scriptorius, and 

 connected by a gray commissure: corresponding therefore to the origins of 

 the Pueumogastric Nerves, which are the principal excitor nerves that con- 

 vey the stimulus on which the movements are dependent, whilst from the 

 adjacent parts of the Medulla Oblongata and Spiualis proceed the chief 

 motor nerves by which they are carried into effect. And thus it happens 

 that the whole of the Eucephalon may be removed from above, and the 

 spinal cord (as far up as the origin of the phrenic nerve) from below, with- 

 out suspending the most essential of the respiratory movements ; the de- 

 struction of these centres, however, causes their immediate cessation, and as 

 the arrest of respiration is incompatible with life, they were named by 

 Floureus the "noeud vital." The Respiratory Centres, as Ducheune 6 has 

 pointed out, are in immediate contiguity to the hypoglossal nucleus goverii- 



1 V. Ghcrt has shown that, during violent exertion, the respirations increase in 

 frequency more than the pulsations; but that in the subsequent period of rest, the 

 increased activity of the cardiac movements is more persistent than that of the respi- 

 ratory. For a list of the number of Respirations per minute in a great number of 

 different animals see P. Bert, Lemons, p. 393 et seq. 



2 Src n 1'nper by Dr. Hooker, an abstract of which will be found in the British and 

 Foreign Medical Review, vol. iv, p. 263. 



' Physiology, p. 215, note. 



4 Memoires de la Soc. de Biologic, 1865, p. 175. Bert (Lemons, p. 410) shows 

 that many statements, though accurate when the obstacle to respiration is slight, 

 must be accepted with some reservation when the obstacle is great, the amplitude 

 then decidedly diminishing. 



5 See Longet (Physiologic, 1861, vol. ii, p. 396), Flourens (Comptes Rendus, 1851, 

 p. 437, and 1858), Brown-Sgquard (Journal de la Physiologic, vol. i, 1858, p. 232), 

 Schiff (Physiologic, 1859, p. 323). 



6 De 1'Electrisation Localises, 1872, p. 564. 



