7 H THE CEREBRAL CORTEX. 



The effects on respiration produced by stimulation of this region 

 have been worked out by W. G. Spencer. 1 He found in the dog, cat, 

 and rabbit, definite spots on the frontal lobe, excitation of which produce 

 respectively (1) slowing and arrest of respiration, (2) acceleration, (3) 

 inspiratory clonus, and (4) inspiratory tonus. The first of these is, 

 in all animals tested, related with the part of the lower surface 

 of the frontal lobe with which the olfactory lobe is connected, and a 

 similar effect on respiration is obtained by stimulating, on the cut 

 section of a hemisphere, the fibres of the anterior commissure. The 

 arrest may occur in inspiration or expiration. When it occurs in 

 inspiration, it is accompanied by a great rise of blood pressure. 



Acceleration was obtained in the dog and cat by stimulation of the 

 upper end of the supra-orbital sulcus, and in the rabbit by excitation 

 of a point on the dorsal surface of the frontal lobe close to the longi- 

 tudinal fissure. Inspiratory clonus was obtained from the junction of 

 the olfactory bulb and tract, inspiratory tonus from many parts of the 

 cortex, but most markedly from the middle of the motor area. 



Most of these results are intimately related to the olfactory region 

 of the cerebral cortex, and are probably to be referred to excitation of 

 the tract which conveys olfactory sensations towards the lower centres 

 (racinc moyenne of Broca). Spencer has himself shown that, except 

 the inspiratory tonus effects (which follow the course of the pyramidal 

 tract fibres), the other effects which he has described are trace- 

 able, by the excitation method, to the tegmental region. Probably, 

 therefore, the points enumerated are not to be regarded as specific 

 respiratory centres, but the movements obtained by their excitation 

 are such as are ordinarily associated with stimulation of the olfactory 

 nerve-endings, and are correlated with activity of the olfactory nervous 

 apparatus. 



Influence of cerebral excitation upon the circulation. Schiff 2 

 was the first to notice the effects on the circulation produced by 

 excitation of the cortex, and they were subsequently (in 1875) shown 

 by Vulpian to be of constant occurrence. Danilewsky 3 obtained, on 

 stimulation in dogs of the suprasylvian gyrus, vaso-constriction and 

 cardio-inhibition. Bochefontaine 4 showed that general vaso-constric- 

 tion, usually accompanied by cardiac inhibition, but sometimes by 

 cardiac acceleration, was produced by excitation of any part of the 

 motor area ; observations which were confirmed by Blchet, 5 who, however, 

 obtained these results chiefly from the anterior part of the sigmoid 

 gyrus. On the other hand, Brown-Sequard, 6 using heat as a source of 

 excitation, obtained manifestations of vaso-dilatation. I myself, in 

 some experiments (hitherto unpublished), performed several years since 

 in conjunction with J. E. Bradford, constantly obtained vaso-dilatation 

 as the result of stimulating certain regions of the cerebral cortex in 

 monkeys ancesthetised by chloroform or chloral, notably the mesial 

 surface of the hemisphere anteriorly (gyrus marginalis and gyrus 



1 Phil. Trans., London, 1894, vol. clxxxv. B, p. 609. 



2 Quoted by Francois-Franck, " Lecon.s sur les fonctions motrioes du cerveau," Paris, 

 1887, p. 163. 



3 Arch.f. d. </es. Physiol., Bonn, 1875, Bd. xi. S. 128. 



4 Arch, dephysiol. norm, etpath.. Paris, 1876, p. 142; 1883, p. 34. 



5 These de Paris, 1878. 



6 Quoted from Francois-Franck, " Lecons sur les fonctions motrices du cerveau," Paris, 

 1887, p. 167. 



