( m ) 



for a time. Then generally one or more sighs follow, after which 

 normal respiration is restored. 



The N. infra-orbitalis rami supra-maxillaris N. trigemini answers 

 to the excitation by a change of respiration different from that 

 produced by stimuhitiou of the N. opticus, but also differing 

 at least in some measure, from the effect of the excitation on the 

 first branch of tliis Nerve. The effect, even when but very weak 

 currents are used, is always the same, a strong permanent inspi- 

 ratory situation of thorax, accompanied by very quick respiration 

 (Fig. 4). The tracing of the respiration differs, in this case, from 

 the maximal sigh-like inspiration produced by stimulating the optic 

 nerve, by its permanence, and by the after-effect, which is a forced 

 expiration and long duration of the quickened rhythm. It differs also 

 from the tracing produced by excitation of the first branch, the 

 quickening here taking place in a more marked manner and during 

 permanent deep inspiratory position of the thorax, and the after-effect 

 also being more marked and lasting longer. 



These facts prove, that the effect of excitation of the N. opticus and 

 of the N. trigeminus on respiration cannot be so simply formulated 

 as CHRibTiANi 1) did by saying that excitation of the optic Nerve 

 produced an inspiratory, that of the N. trigeminus an expiratory effect. 



Faradic excitation of the three nerves mentioned, always accelerate 

 the respiration, that is to say, each of them exercises the same 

 influence on the second of the inspiratory effects above mentioned, 

 but each of them lias a somewhat different effect on the first of 

 the so called inspiratory effects i. e. on the deepening of the inspiration. 



The faradic excitation of tlie optic Nerve calls forth the maxi- 

 mal deep inspiration, directly followed by lengthened expiration, 

 suppressed as long as the stimulus lasts — what we have called 

 sigh — , that oi the first branch of the N. trigeminus produces none 

 or Ycry little effect, it increases slowly the inspiratory position of 

 the thorax, that of the second branch of this Nerve maintaina the 

 thorax in a permanent and maximally extended state. 



The different tracings of respiration, obtained during excitation of 

 the nerves, make it advisable to suppose that two different inspira- 

 tory effects, acceleration of rhythm and deepening of amplitude, exist. 



The deepening of the amplitude however may appear in two forms 1", 

 as the quick, maximally deep inspiration followed by a suppression 



') Arthue Christiani. Ueber Athmungscentra und centripetale Atlimiiugsnerven. 

 Monatsbericlite der königlich preussischeu .\kade;iiie der VVissenscliafteu zu Berlin. 

 1&82. (Sitz. 17 Febr. 1881). S. 213. 



