466 PHYSIOLOGY CHAP. 



attaches to another group of reflexes, which till now have been 

 little considered by physiologists, i.e. those reflexes determined by 

 the impulses which originate in the afferent nerves to the 

 respiratory muscles. 



In speaking of concomitant respiratory movements (p. 421) 

 we said that in many animals each inspiratory act is accompanied 

 by active dilatation of the glottis and nostrils, while constriction 

 of these apertures accompanies each act of expiration. E. du 

 Bois - Eeymond and Katzenstein (1901) observed in dogs that 

 these movements of the glottis may appear also in double pneunio- 

 thorax, or when the lungs are retracted. Under these conditions 

 they noted that the passive compression of the thorax (expiratory 

 position) determined a constriction, while the elastic return to the 

 inspiratory position determined active dilatation of the glottis. 

 From this they inferred that these effects depend on changes in 

 the position of the thorax In all probability this is an example 

 of co-ordination of reflexes by way of the sensory muscular and 

 tendinous inner vation, which, as we shall see in Vol. III., has been 

 worked out by Sherrington for locomotor movements. 



The two authors named above have indicated another fact of 

 great importance to the theory of central respiratory innervation. 

 They described the concomitant respiratory movements of the 

 vocal cords with intact thorax during the movements of the 

 diaphragm determined by excitation of the phrenic in the neck. 

 Under these conditions they saw that the tetanic stimulation of 

 one or both phrenics determined movements of adduction in the 

 vocal cords. The contraction of the diaphragm preceded by an 

 appreciable interval the closure of the glottis, which lasted as 

 long as the stimulation of the phrenic. They interpreted these 

 reflexes as due to excitation of the pulmonary fibres of the vagus, 

 which tallies with the auto -regulatory theory of Hering and 

 Breuer. 



Mislawsky (1892) also communicated to the International 

 Physiological Congress at Turin, a reflex action of quite similar 

 character, as established by the work of his pupil Luria. Excita- 

 tion of the tendinous centre of the diaphragm determines expira- 

 tory arrest of the thorax. Stimulation of the peripheral trunk of 

 the phrenic nerve has the same effect. Here, again, as in the 

 case of E. du Bois - Eeymond and Katzenstein, we have an 

 inspiratory act (contraction of the diaphragm) determining 

 reflexly an expiratory act (adduction and closure of the vocal 

 cords, expiratory position of thorax). Mislawsky, too, holds that 

 these reflexes are completed by way of the pulmonary vagi. As a 

 matter of fact they disappear after section of the vagi. 



Baglioni (1903) in his study of the same reflexes took into 

 consideration the afferent nerve paths, which, as we have seen, run 

 in the phrenic nerves along with the afferent fibres. 



