VARIATIONS OF THE RESPIRATORY MOVEMENTS. 233 



that the costal type occurs in children of both sexes, and they ascribe as a cause 

 the greater flexibility of the ribs of children and women, which permits the 

 muscles of the chest to act more efficiently upon the ribs. [When a child sucks, 

 it breathes exclusively through the nose, hence catarrhal conditions of the nasal 

 mucous membrane are fraught with danger to the child.] 



111. Pathological Variations of the Respiratory 

 Movements. 



I. Changes in the mode Of movement. In persons suffering from disease of 

 the respiratory organs, the dilatation of the chest may be diminished (to the 

 extent of 6 or 5 cmtr. ) on both sides or only on one side. In affections of the apex 

 of the lung (in phthisis), the sub-normal expansion of the upper part of the wall of 

 the chest may be considerable, detraction of the soft parts of the thoracic wall, 

 the xiphoid process and the parts where the lower ribs are inserted, occurs in 

 cases where air cannot freely enter the chest during inspiration, e.g., in nar- 

 rowing of the larynx; when this retraction is confined to the upper part of the 

 thoracic wall, it indicates that the portion of the lung lying under the part so 

 affected is less extensile and diseased. 



Harrison's Groove. In persons suffering from chronic difficulty of breathing, 

 and in whom, at the same time, the diaphragm acts energetically, there is a slight 

 groove which passes horizontally outwards from the xiphoid cartilage, caused by 

 the pulling in of the soft parts and corresponding to the insertion of the diaphragm. 



The duration of Inspiration is lengthened in persons suffering from narrowing of 

 the trachea or larynx ; expiration is lengthened in cases of dilatation of the lung, 

 as in emphysema, where all the expiratory muscles must be brought into action 

 (Fig. 104). 



II. Variations in the Rhythm. When the respiratory apparatus is much 

 affected, there is either an increase or a deepening of the respirations, or both. 

 When there is great difficulty of breathing, this is called Dyspnoea. 



Causes Of Dyspn03a. (1) Limitation of the exchange of the respiratory gases 

 in the blood due to (a) Diminution of the respiratory surface (as in some diseases 

 of the lungs); (&) narrowing of the respiratory passages; (c) diminution of the red 

 blood-corpuscles; (d) disturbances of the respiratory mechanism (e.gr., due to affec- 

 tions of the respiratory muscles or nerves, or painful affections of the chest-wall); 

 (e) impeded circulation through the lungs due to various forms of heart-disease. 

 (2) Heat-dyspnoea. The frequency of the respirations is increased in febrile con- 

 ditions. The warm blood acts as a direct irritant of the respiratory centre in 

 the medulla oblongata, and raises the number of respirations to 30-60 per minute 

 (" Heat-dyspnoea"). If the carotids be placed in warm tubes, so as to heat the 

 blood going to the medulla oblongata, the same phenomena are produced (A. 

 Fick.) See also " Respiratory centre" (vol. ii.). 



Cheyne-Stokes' Phenomenon. This remarkable phenomenon occurs in certain 

 diseases, where the normal supply of blood to the brain is altered, or where the 

 quality of the blood itself is altered, e.g., in certain affections of the brain and heart, 

 and in ursemic poisoning. Respiratory pauses of one-half to three-quarters of a minute 

 alternate with a short period (^-f min.) of increased respiratory activity, and during 

 this time 20-30 respirations occur. The respirations constituting this ' ' series" are 

 shallow at first ; gradually they become deeper and more dyspno?ic, and finally 

 become shallow or superficial again. Then follows the pause, and thus there is an 

 alternation of pauses and series (or groups) of modified respirations. During the 

 pause, the pupils are contracted and inactive; and when the respirations begin, they 

 dilate and become sensible to light ; the eyeball is moved as a whole at the same 

 time (Leube). Hein observed that consciousness waa abolished during the pause, 



