ix MID- AND INTER-BRAIN 513 



action by mechanical stimuli, to which the centres are highly 

 sensitive. He found, in fact, that on employing electrical ex- 

 citation, which is more easily graduated and less destructive 

 than these injurious stimuli, the clasp is never interrupted, but 

 is actually strengthened. On the other hand the local application 

 of an anaesthetic, e.g. stovaiiie, to the dorsal surface of the optic 

 lobes is followed by interruption of the embrace. 



In birds electrical stimulation of an optic lobe causes dilatation 

 of the pupil on the opposite side ; the head is also raised, and 

 various movements are made by the wing on the opposite side, 

 and by both feet (Ferrier). 



Kschischkowski has recently (1911) in our laboratory employed 

 Baglioiii's method of specific chemical stimuli (strychnine and 

 carbolic acid) applied locally, in order to discover the nature of 

 the central elements which constitute the superficial layers of the 

 optic lobes in the pigeon. He found that the application of 

 strychnine and picrotoxin caused contraction of the skeletal 

 muscles of the fore- and hind -limbs and of the neck on the 

 opposite side. It is only when the poison is applied in larger 

 quantities or to a greater surface (1-2 sq. mm.) that contractions 

 of the homolateral muscles with circus movements towards the 

 same side occur. These phenomena of excitation set in a few 

 seconds after the application of the stimulus and last for some 

 minutes. Since the application of carbolic acid has no effect, we 

 may conclude that the elements of the superficial layer of the 

 optic lobes are, in relation to this chemical stimulus, of the same 

 character as the central elements of the dorsal half of the cord, 

 as well as the cells in the excitable cortex of the dog, since these 

 also have the specific property of reacting to strychnine and 

 picrotoxin and not to carbolic acid, which, on the other hand, 

 produces a reaction from the motor cells of the ventral horn (see 

 above, pp. 264 et seq.}. 



In mammals faradisation of the anterior quadrigeminal body 

 produces pupillary dilatation on the opposite side, and at a later 

 stage on the same side also, and conjugate deviation of the eyes 

 upward and towards the opposite side, with retraction of the ear 

 and angle of the mouth. The same stimulus applied to the 

 posterior quadrigeminal body produces erection of the ear on the 

 opposite side and emission of cries. ' 



Adamuk succeeded in producing different co-ordinated move- 

 ments of the eyes when he excited various points of the anterior 

 quadrigeminal bodies in the dog. After a vertical section in 

 the median plane the reaction only involves the eye' of the side 

 excited. 



Terrier, experimenting on monkeys, obtained similar reactions 

 to those seen in dogs. Unilateral electrical excitation of the 

 anterior quadrigeminal body produces wide dilatation of the 



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