DEGENERATIONS FROM LESIONS OF TEMPORAL CORTEX. 153 



tapetum (see d. 3, fig. 3), and at once separated into two groups. 

 One of these remained on the side proximal to the lesion, and 

 passed back into the occipital lobe, forming a layer immediately 

 outside the posterior horn of the lateral ventricle. The other 

 crossed over in the corpus callosum, and was found in the 

 tapetum of the opposite side, along which its fibres were traced 

 backwards and downwards into the occipital lobe, forming here 

 also a layer placed closely external to the posterior horn (see 

 d. ^, fig. 4), and internal to the so-called optic radiations of the 

 white centre. In this way a communication is estabhshed 

 between a given area of temporal cortex and the surfaces of 

 both occipital lobes. 



Some light is also thrown upon the constitution of the 

 tapetum, concerning which a good deal of difference of opinion 

 exists amongst cerebral investigators. Wernicke^ believed it 

 to be a set of fibres passing from the corpus callosum into the 

 internal capsule. Dejcrine,- however, identifies it with the 

 occipito-frontal fascimlus of ForeV^ and Onufrowicz; but, while 

 denying that it receives any fibres from the corpus callosum, or 

 contributes any to the internal capsule, he admits that it is made 

 up of fibres from two different sources. Where the second set 

 of fibres originates, Dejerine does not state. Mingazzini^ 

 corroborates the view that the tapetum contains two sets of 

 fibres, one of which belongs to the fasciculus occipito-frontalis ; 

 the other is furnished by the corpus callosum. Dotto and 

 Pwsa^eri 5 have also found that the corpus callosum contributes 

 fibres to the tapetum. My own results fully substantiate this 

 latter view, and further show at least one source from which 

 the callosal fibres come. They do not lend any support to the be- 

 lief that fibres of the tapetum descend into the internal capsule. 



(&) Anterior Comiiiissure. — In all cases where the lesion of the 



1 Wernicke, Lehrbuch d. GeUrnkrcmkheiten, Leipzig, 1881. 



■•^ Dejerine, J., Anafomie des Centres Ncrveux, Tome 1, p. 760, Paris, 1895. 



=' Forel, " Fall von Mangel d. Balkens in einem Idiotenhirn," Tagebl. d. 54. 

 Versamml. deutsch. Natnrforsch. u. Aertzte in Salzburg, 1881. 



^ Mingazzini, G., " Osservaz. Anat. intorn al corpo callose e ad alcuuo formaz. 

 che con esso hanno rapporto," iJiVcre/i. lah. di Anat. Norm. Univ. Roma., vol. 

 vii. pp. 5-28. 



5 Dotto and Pusateri, " Sul decorso delle fibr. del corp. callos. e del psalteriuni," 

 Rivist. dipatol. Nerv e ment., ii. 2, 1897. 



