112 VETERIXARY PHYSIOLOGY 



of tickling is lost, not with tactile sense, but with the sense 

 of pain. 



The upgoing fibres in the lateral columns may thus be 

 sorted out into, five sets as is shown in fig. 49, 



They may be called — 



1. The direct cerebellar tract, B. 



2. The anterior cerebellar tract, C. 



3. The lateral spino-thalamic, D. 



4. The spino-tectal. 



5. The anterior spino-thalamic, E. 



Injury to the posterior columns causes a marked loss of 

 the muscle-joint sense and of tactile sense for some distance 

 below the lesion. 



The fibres from each of the several kinds of receptors in 

 the body which run side by side in the nerves are thus 

 sorted out ■physiologically in the spinal cord by passing 

 through synapses — (1) Those from pain receptors being sent 

 up a definite tract in the lateral column (fig. 49). (2) 

 Those from temperature receptors passing along with the last. 

 (3) Those from tactile receptors passing up the posterior 

 columns for a considerable distance before forming synapses 

 and after crossing the middle line (fig. 48) being grouped 

 at the anterior margin of the cord. (4) Those from the 

 proprioceptive receptors of muscles and joints (a) passing 

 up the posterior cokimns to the top of the cord before form- 

 ing synapses from which fibres lead up the brain-stem and 

 finally to the cortex cerebri ; (6) forming synapses in the 

 grey matter of the cord in Clark's vesicular column, from 

 which fibres run up in the two cerebellar tracts to the 

 cerebellum (p. 127). 



3. Connections with the Brain-Stem and Cerebrum. 



These various fibres from the synapses in or above the 

 cord which pass up the brain-stem end by synapses — 



A, in the tectum (T, fig. 58), 



B. in the thalamus (Th, fig. 58), 



