CORPUS STRIATUM OF MAMMALS 115 



onic mammals, and the corpus striatum laterale of 

 Hines's figures (1922) of the developing human brain. 

 In adult mammals the new striatum loses its identity 

 as a separate lobe of the striatum. Most of its tissue 

 is joined to that of the olfacto-striatum (bed nucleus 

 of stria terminalis of Johnston, 1923) to form the 

 definitive caudate nucleus, and a smaller part is 

 contributed to the putamen and claustrum. 



The functions of the new striatum of lower mam- 

 mals have not been clarified. In reptiles and birds 

 the corresponding structures are evidently transi- 

 tional, both anatomically and physiologically, be- 

 tween the old striatum and the cerebral cortex. This 

 transitional hypopallium and the related cerebral 

 corte?^ exert some sort of reinforcement or augmenta- 

 tion upon some behavior sequences and some measure 

 of inhibition upon other sequences. They are also 

 concerned with the synthesis of elementary reflexes 

 into more complex instinctive cycles and with increase 

 in the range and variety of reactions to exteroceptive 

 stimulation (Rogers). With amplification of the cor- 

 tex in lower mammals the second group of these func- 

 tions seems to have been taken over wholly by the 

 cortex and the first in part. The more intimate fusion 

 of the new striatum with the old striatum results in 

 a complex organ whose functions seem to be pre- 

 dominantly dynamogenic. 



There is some evidence that the mammalian 

 striatum exerts some control over various visceral 



