20 Veterinary Medicine. 



15. Stimulation of the convolution in front of the crucial fis- 

 sure, on its anterior and sloping portion, causes movements of 

 the phar^'nx and larynx (swallowing). 



16. Stimulation of motor areas of the cortex, by scraping, irri- 

 tation, or disease tends to produce spasmodic contractions of cer- 

 tain groups of muscles (Jacksonian Epilepsy). vStrong stimula- 

 tion may cause general epileptiform spasms, which are at first 

 tonic, then clonic. One such seizure strongly predi.sposes to a 

 second. If, during an attack, the cortical centres presiding over 

 a special group of mu.scles were sliced off, such mu.scles relaxed, 

 though the general spasms in the other muscles continued. 



Localizations of Spinal Lesions. 



Being at once a conductor between the brain and nerves, and a 

 reflex nerve centre, we must consider both roles in seeking to 

 locate lesions from symptoms. In passing from the nerves to 

 and from the sensorium both sensory and motor currents cross so 

 that one side of the brain presides over the other side of trunk 

 and limbs. This crossing of the motor fibres takes place in the 

 medulla oblongata, while that of the sensory fibres occurs in the 

 spinal cord clo.se in front of the nerve from which the}^ have 

 entered. 



Cross-Section of one lateral half of the spinal cord 

 therefore causes motor paralysis and rise of temperature of the 

 whole of that side of the body posterior to the lesion, wliile it in- 

 duces sensor}' paralysis and cooling on the opposite side of the 

 body up to the same point. A very limited sen.sory paral3^sis on 

 the same side occurs corresponding to the few sensory fibres pass- 

 ing outward obliquely through the portion injured by the cross- 

 section. 



A vertical section of the cord separating the one lateral 

 half from the other does not necessarily affect the motor cur- 

 rents, while it produces a limited anse.sthesia on each side in the 

 area of distribution of the nerves, the .sensory fibres of which 

 cro.ssed in the seat of the lesion. 



Transverse section of the superior columns causes hyper- 

 sesthesia and lack of coordination. 



Transverse section of inferior columns, or of the in- 

 ferior horn of gray matter, if close behind the medulla, cau.ses no 



