PSYCHICAL FUNCTIONS OF THE BRAIN. 68 1 



and in rare cases the excitability is unequal on the two sides, as is manifested by 

 unilateral perspiration ( 289, 2). 



Poisons. Calabar bean, nicotin, picrotoxin, camphor, and ammonium acetate, cause a 

 secretion of sweat by acting directly on the sweat-centre. Muscarin causes local stimulation of 

 the peripheral sweat-fibres it causes sweating of the hind limbs after section of the sciatic 

 nerves. A tropin arrests the action of muscarin {Ott, Wood, Field, Nawrocki). 



[Regeneration of the Spinal Cord. In some animals, true nervous matter is reproduced after 

 part of the spinal cord has been destroyed, at least this is so in tritons and lizards {H. MiLller). 

 In these animals, when the tail is removed, it is reproduced, and Miiller found that a part of 

 the spinal cord corresponding to the new part of the tail is reproduced. Morphologically, the 

 elements were the same, but the spinal nerves were not reproduced, while physiologically, the 

 new nerve substance was not functionally active ; it corresponds, as it were, to a lower stage of 

 development. According to Masius and Vanlair, an excised portion of the spinal cord of a frog 

 is reproduced after six months ; while Brown-Sequard maintains that re-union of the divided 

 surfaces of the cord takes place in pigeons after six to fifteen months. A partial re-union is 

 asserted to occur in dogs by Dentan, Naunyn, and Eichhorst, although Schieferdecker obtained 

 only negative results, the divided ends being united only by connective-tissue (Schwalbe).] 



374. PSYCHICAL FUNCTIONS OF THE BRAIN. The hemispheres of 

 the cerebrum are usually said to be the seat of all the psychical activities. Only 

 when they are intact are the processes of thinking, feeling, and willing possible. 

 After they are destroyed, the organism comes to be like a complicated machine, and 

 its whole activity is only the expression of the external and internal stimuli which 

 act upon it. The psychical activities appear to be located in both hemispheres, so 

 that after destruction of a considerable part of one of them, the other seems to act 

 in place of the part destroyed. [Objection has been taken to the term the "seat 

 of " the will and intelligence, and undoubtedly it is more consistent with what we 

 know, or rather do not know, to say, that the existence of volition and intelligence 

 is dependent on the connection of the cerebral cortex with the rest of the brain.] 



[That a certain condition of the cerebral hemispheres is necessary for the manifestation of the 

 intellectual faculties, is admitted on all hands ; for, compression of the brain, e.g., by a depressed 

 fracture of the skull, and sudden cessation of the supply of blood to the brain, abolish conscious- 

 ness. The intellectual faculties are affected by inflammation of the meninges involving the 

 surface of the brain, the action of drugs affects the intellectual and other faculties ; but while 

 all this is admitted we cannot say precisely upon what parts of the brain ideation depends. The 

 pre-frontal area, or the convolutions in front of the ascending frontal supplied by the anterior 

 cerebral artery, are sometimes regarded as the anatomical substratum of certain mental acts. 

 At any rate, electrical stimulation of these parts is not followed by muscular motion, and, 

 according to Ferrier, if this region be extirpated in the monkey, there is no motor or sensory 

 disturbance in this animal ; it still exhibits emotional feeling, all its special senses remain, and 

 the power of voluntary motion is retained ; but, nevertheless, there is a decided alteration in 

 the animal's character and behaviour, so that it exhibits considerable psychological alterations, 

 and, according to Ferrier, " it has lost to all appearance the faculty of attention and intelligent 

 observation. "] 



Observations on Man. Cases in which considerable unilateral lesions or destruction of one 

 hemisphere have taken place, without the psychical activities appearing to suffer, sometimes 

 occur. The following is a case communicated by Longet : A boy, 16 years of age, had his 

 parietal bone fractured by a stone falling on it, so that part of the protruding brain-matter had 

 to be removed. On reapplying the bandages, more brain-matter had to be removed. After 18 

 days he fell out of bed, and more brain-matter protruded, which was removed. On the 35th 

 day he got intoxicated, tore off the bandages, and with them a part of the brain-matter. After 

 his recovery, the boy still retained his intelligence, but he was hemiplegic. Even when both 

 hemispheres are moderately destroyed, the intelligence appears to be intact ; thus, Trousseau 

 describes the case of an officer whose fore-brain was pierced transversely by a bullet. There 

 was scarcely any appearance of his mental or bodily faculties being affected. In other cases, 

 destruction of parts of the brain peculiarly alters the character. We must be extremely careful, 

 however, in forming conclusions in all such cases. [In the celebrated "American crow-bar 

 case " recorded by Bigelow, a young man was hit by a bar of iron 1| inch in diameter, which 

 traversed the anterior part of the left hemisphere, going clean out at the top of his head. This 

 man lived for thirteen years without any permanent alterations of motor or sensory functions ; 

 but ' ' the man's disposition and character were observed to have undergone a serious change. 

 There were, however, some changes which might be referable to injury to the frontal region." 

 In all cases it is most important to know both the exact site and the extent of the lesion. Ross 



