( 369 ) 



parts of the tractus. Theiefore it is easier to find it at the points 

 f and (J of our diagram, where the tractus and lobus olfactorius 

 reach each other, instead of exposing the basal surface of the brain, 

 which is much more difficult. 



Perhaps this is the reason why Spencer does not state, that the 

 expiratory effect, we now shall describe, may be produced by exci- 

 tation of the olfiictory bulb. 



There is still another point, wherein our results differ from those 

 of ÖPENCER. This author obtains "arrest" (and it sometimes takes 

 place in inspiration, sometimes in expiration) at the beginning of 

 the excitation with rather strong currents, and as soon as the sti- 

 mulation stops, the "arrest" ends. 



We observed, that even weak currents (10 cm. distance between 

 the two coils) and even better currents of moderate strength (8 — 6 cm.) 

 exciting the points /', g^ or the basal middle part of the tractus and 

 the bulbus olfactorius, produce the following effects. 



The respiration may become slower (Fig. 7). In general however, 

 after a few slow lespirations, the thorax gains the position of expi- 

 ration, and at last "■arrest in ex2)iration" takes place. This arrest 

 may occur before the stimulus (during 10 seconds generally) ceases, 

 but more often this arrest begins only a few seconds later. It may 

 then last half a minute and longer. The current not being stopped, 

 the arrest sets in, and may last for 1 or 2 minutes; ultimately 

 deep inspirations set in. 



If the currents last 10 sec. only, the arrest often begins after 

 they have ceased, is prolonged 15 to -15 seconds, and then a few 

 superficial respirations appear (often only visible in the tracing of 

 the trachea-respiration), the thorax meanwhile taking an inspiratory 

 position. This period may be indicated by a few inspirations only, 

 (Fig. 9) at other times the thorax abruptly takes an inspiratory 

 position and remains a long time in it, some irregular and super- 

 ficial respirations coming between (Fig. 10), and often the thorax 

 reaches its inspiratory position only very slowly after a greater 

 number of irregular, superficial, gradually deepening respirations 

 (Fig. 11 upper tracing). At the end one or two deep sighs appear, 

 followed by very deep and slow respirations. 15 minutes and more 

 may elapse before all has returned to the normal condition. 



The arrest and the described mechanism of compensation of the 

 arrest — as we have called this after-eftect, because it may be supposed 

 that deepening of the inspiration, compensates the arrest in expira- 

 tion — may be called forth, by exciting the points /"and (/ with the 

 utmost constancy. With no greater constancy are the movements in 



