THE NERVOUS SYSTEM OF THE BIRD 189 
A short tract in the anterior columns which does not quite reach the middle line ; this 
system is probably internuncial in nature, connecting different levels of the spinal cord. 
Descending, — The descending tracts occupy both the anterior and lateral columns in the 
same relative position as the direct and crossed pyramidal system of Mammals, and extending 
downwards into the lumbar region. This description agrees in all respects with that of Munzer 
and Wiener. 
A. Friedlander,* who has recently studied the degenerations following lesions of the 
spinal cord in the Bird, takes a different standpoint. 
He holds that there are no distinct system tracts in the cord, but that fibres of an inter- 
nuncial nature ascend and descend in the same region. As, however, indicated we cannot accept 
this opinion. 
PHYSIOLOGICAL 
The anatomical features which we have described bring out four salient facts : — 
(1) The absence of any tracts extending to the spinal cord from the cerebral hemispheres. 
(2) The paramount importance of the tracts from the cerebral hemispheres to the 
mesencephalon. 
(3) The extensive connection existing between the corpus striatum and the thalamus. 
(4) The importance of the mesencephalon both as a reflex centre and as the seat of origin 
of important spinal tracts. 
(l) The Absence of Tracts extending from the Hemisphere to the Cord. — Such a system of 
fibres, according to Edinger, first makes its appearance in Mammals. This author remarks, 
' Der Fuss ist ein novum additum, das erst sehr spat in dem Thierreiche erscheint' (' Vorlesungen.' 
1896). No trace is found in Fishes, Reptiles, or Birds, it appears pari passu with the great 
development of the cortex, and the entire absence in these animals of any noted defect of 
movement after removal of one hemisphere, accords with this anatomical fact. That the cerebral 
hemisphere, however, does exercise a great influence over the rest of the nervous system, is shown 
by the condition of pigeons in which both hemispheres have been removed. Tliis has been made 
the subject of an elaborate study by ScHRADER.t 
We can fully confirm the description this observer gives of the symptoms, which vary 
according to the time which has elapsed since the operation. After recovering from the operation 
the animal is markedly inert, standing with ruffled feathers and bent head ; its eyes are shut, and 
the animal pays no attention to noises, nor when the eyelids are open does the movement of objects 
in the field of vision produce any effect ; when touched the animal makes a few steps forward 
and then comes to a standstill. There is complete loss of initiative ; when thrown into the air 
it obtains some kind of support from its wings, but the appearance is more of falling than flying. 
It does not pick corn, and must be fed. After several days this condition of lethargy passes away 
and is replaced by constant walking aimlessly about, — as Schrader says, the animals wander 
ceaselessly to and fro. They are capable of perching, and adjust their balance when placed in a 
* Friedlander, loc. cit. 
■\ Schrader, ' Prtiiger's Arch.,' vol. 55, pp. 44, 175. 
