416 



PHYSIOLOGY 



CHAP. 



regular and measurable tracings of the variations of the thoracic circum- 

 ference. It is one of the instruments most employed for clinical purposes. 



Eosenthal's phrenograph is used to obtain exact tracings of the excursions 

 of the diaphragm. It consists in a spatula-shaped lever, applied, aftef/ 

 making an opening in the median line of the epigastrium, to the concave 

 vault of the diaphragm. A simpler method is that which introduces a flat 

 elastic rubber bag between the diaphragm and the abdominal organs, which 

 is: compressed when the diaphragm contracts, and decompressed on its 

 relaxation, these effects being transmitted to a Marey's writing tympanum 

 (Foster). This method records not only the movements of the diaphragm, 



but also the alternate contrac- 

 tions of the abdominal muscles. 

 The simplest method, which 

 involves 110 vivisection, and is 

 therefore applicable to man, 

 consists in applying the button 

 of an exploring tympanum, 

 or of Vierordt's sphygmo- 

 graph, or of Burdon-Sander- 

 son's cardiograph (Fig. 107, 

 p. 267) to any point of the 

 epigastrium. In man (who, 

 as we shall see, breathes with- 

 out active intervention of the 

 abdominal muscles) this 

 method yields fairly satis- 

 factory results. 



VI. After defining the 

 inspiratory and expiratory 

 muscular mechanisms, on 

 which depend the rhyth- 

 mical expansion and 

 contraction of the thor- 

 acic cavity, we next have 

 to determine which of 

 these intervene and have 

 a preponderating action 

 during normal respiration, 



FIG. 183. Diagram of variations of antero - posterior an( J wn i cn come HltO 



TV' 



. 



diameter of thorax and abdomen in the two sexes 

 during normal breathing and forced respiration, m lorCCd Or 



respiratory rhythm. 



Even in ordinary quiet breathing two types of respiratory 

 movements can be distinguished, the abdominal and the costal ; 

 in the former the activity of the diaphragm is the more pro- 

 nounced, in the latter that of the external in tercostals, or generally 

 speaking, of the muscles by which the ribs are elevated. 



According to Hutchinson's observations (1852), a man's 

 breathing is always abdominal, a woman's costal. By drawing on 

 a flat plane the outline of the shadows projected by two persons 

 of different sex, at the several moments of normal or forced 

 respiratory movements, he obtained the diagrams of Fig. 183, 

 which illustrate very effectively the two types of respiration. 



