1909.] Coi'tical Lamination, etc., in Brain of Marmoset. 131 



of the cortex lying immediately round the corpus callosum, from its anterior 

 to its posterior genu. Sections cut through the hippocampal fissure show a 

 narrow strip of cortex having the same structure bordering the olfactory type, 

 lying between it and the distinctive structures of the hippocampal fissure. It 

 is probable that, as in the Lemur, a narrow strip of limbic cortex is to be 

 found curving around the posterior genu of the corpus callosum, and folding 

 in to the hippocampal fissure, thus forming a link between the upper and 

 lower portions of the limbic lobe. 



Characteristics. — The cortex measures 0*8 mm. to I'O mm., the depth of the 

 molecular layer being about 0'2 mm. The remainder of the cortex cannot 

 1)6 separated into layers. The cells immediately beneath the molecular layer 

 have a tendency to be pyramidal in form, but below these the mass of them 

 are blunt, shapeless, and faintly stained, only becoming more angular at the 

 ■bottom of the cortex, in the position of the polymorph layer. 



Localisation of the Motor Area hy Stimulation. 



The animals were anaesthetised either by ether or A.C.E. mixture, and 

 ■anaesthesia was maintained throughout the whole of the operation until the 

 •animals were killed at the conclusion of the experiment. 



In dealing with so small a brain, the parts are so delicate that the greatest 

 possible care has to be exercised throughout. In one experiment the animal 

 ■died from haemorrhage owing to the injury of a vessel entering the longitudinal 

 sinus, in an attempt to separate one hemisphere from its fellow in order to 

 stimulate the mesial surface, and further attempts to explore this portion of 

 the cerebrum were therefore abandoned. 



In the remaining two experiments, in which the greater part of the 

 •external surface of the hemisphere was exposed, we obtained concordant 

 results by the method of stimulation. The stimulating electrodes were finely 

 pointed and very close together ; they were made of platinum and were 



t. 



connected to the secondary coil of a Du Bois Eeymond inductorium arranged 

 for faradisation. The strength of current employed was that which could 

 just be felt as a faint tingling on the tongue. The accompanying illustration 

 (fig. 7) gives the results of these experiments. It represents the left hemi- 

 sphere seen partly from the side and partly from above, to show the excitable 

 area. This will be seen to be situated wholly above and in front of the 

 Sylvian fissure. If the various figures placed on the diagram are compared 

 with the description beneath it, it will be seen that the head area is a large 

 one, and above this are situated the centres for the upper limb and then 

 those for the lower limb, which is the usual arrangement. 



The larger cortical representation of the head and face region enabled one 



