THE CEREBRUM, AND ITS FUNCTIONS. 



705 



guage lias its seat in this particular convolution. Language, however, is co- 

 extensive 'with thought, and the third left frontal convolution is not tin- seal 

 of language as a faculty of the mind, but simply an important link in the 

 nervous mechanism of speech. Dr. Hughlings Jackson 1 has pointed out 

 that language may be intellectual or emotional, arid that when all power of 

 expressing ideas in words is lost, an entire phrase may be uttered under 

 emotion. Intellectual language again or intellectual expression he shows 

 to be a department of educated movements in general, and gives reasons for 

 believing that the entire hemisphere is concerned in its evolution. It con- 

 flicts with all preconceived notions that the left side of the brain should 

 alone have to do with the expression of ideas in language, but this seems to 

 be clearly demonstrated by Pathology. P. Broca and Dr. Moxon have 

 explained it by supposing that the side of the brain only is educated, and 

 Gratiolet's observation that the left frontal convolutions are developed before 

 the right, has been adduced in support of this view, which, however, cannot 

 be said to be established. The mechanism of speech and thought may be 

 represented as follows. Impressions derived from sensory surfaces generally 

 (GS, Fig. 248) and from the organs of special sense (OA) are translated in 

 the sensory ganglia of the base of the brain (OT) into sensations. These 

 sensations transmitted upwards to the cortex of the hemispheres here give 

 rise to perceptions, or the intellectual recognition of the external causes of 

 the sensations ; by combination again of the different perceptions derived 

 from a given object an idea or complete intellectual representation of the 

 object is formed, with which is associated a name. The " perceptive centres" 

 (Bastian) in which simple perceptive recognition takes place (PC) are prob- 

 ably situated near the margins of the hemisphere where the convolutions are 

 directly connected by fibres with the central ganglia, while ideas are sup- 

 posed to be formed in the convolutions remote from the margins, many of 

 which receive no fibres from the central ganglia or cms, but are connected 

 by arcuate fibres with the marginal convolutions and with each other. Up 

 to the present the mechanism describ- 

 ed is that concerned in the reception of 

 impressions and the formation and as- 

 sociation of ideas. When these ideas 

 are to be expressed in words the prop- 

 osition is formulated, and the phrase 

 mentally rehearsed in the higher con- 

 volutions, and transmitted for verbal 

 expression to the third left frontal 

 gyrus, the function of which is to pro- 

 vide the appropriate words or motor 

 symbols in which the idea is to be 

 clothed, and call into action through 

 the corpus striatum the motor nerve- 

 nuclei in the medulla which are con- 

 cerned in articulation and phonation. 

 The third left frontal convolution is 

 thus the first step on the way out for 

 words, and damage here leaves the 



Subject of it able 011 the One hand to A. Auditory nerves, o. Optic nerve. GS. Gen- 



understaud what is said, to form ideas, eral s"sory surface. OT. Optic thaiamus PC. 

 and even to rehearse propositions in rr*? t- ic. ideationai centre. . 



, . . , Corpus striatum. 3 FR. Third frontal couvolu- 



his mmd, and on the other hand able tion. MO. Medulla obiongata. 



FIG. 248. 



1 Lancet, Feb. 1866, Dec. 18G7, July and Nov. 1868. 



