PLATE 18 
EXPLANATION OF FIGURES 
73 Transection at the level of the commissura transversa. Weigert method. 
lie 
74 Transection through the same region as is shown in fig. 73. Ramén y Cajal 
method. 46. Shows particularly the tractus preoptico-habenularis, pars 
lateralis. In Petromyzon, according to Johnston (02), alarge portion of the fibers 
of his tractus olfacto-habenularis (my tractus preoptico-habenularis) take this 
course; as is also the case, but to a lesser extent, in amphibians and reptiles (Her- 
rick, 710'b). 
75 Cells of origin of the fasciculus retroflexus, or Meynert’s bundle. Golgi 
method. 93. One of the cells possesses a long neurite which may be traced into 
the fasciculus retroflexus. 
com. trans., commissura transversa; fasc. lat. hem. <——, fasciculus lateralis 
hemisphaeril; fasc. med. hem. <——, fasciculus medialis hemisphaeri; fasc. med. 
n. opl., fasciculus medialis nervi optici; hab., habenula; nucl. preopt., pars 
magnocell., nucleus preopticus, pars magnocellularis; pol. post. hem., polus 
posterior hemisphaerii; tr. hyp. olf. med., tractus hypothalamo-olfactorius 
medialis; tr. olf. hab., tractus olfacto-habenularis; tr. olf. thal. med., pars dors., 
tractus olfacto-thalamicus medialis, pars dorsalis; tr. olf. thal. med., pars 
intermed. <——, tractus olfacto-thalamicus medialis, pars intermedia; ¢r. olf. 
thal. med., pars vent., tractus olfacto-thalamicus medialis, pars ventralis; (r. opt., 
tractus opticus; tr. praeth. cin., tractus praethalamo-cinereus; tr. preopt. hab., 
partes ant. et med., tractus preoptico-habenularis, partes anterior et medialis; 
tr. preopt. hab., pars lat., tractus preoptico-habenularis, pars lateralis; tr. preopt. 
hab., pars post., tractus preoptico-habenularis, pars posterior ;lr. preopt.intermed., 
pars. lat., tractus preoptico-intermedius, pars lateralis. 
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