CCENUROSIS (GID, STURDY, TURN-SICK). 471 



eye appear infected, but examination with the ophthahiioscope reveals 

 lesions of more or less extensive neuro-retinitis. 



The visual disturbance is of central origin. The powers of move- 

 ment may be affected in numerous ways, which at times are extremely 

 difficult to estimate with accuracy. Sometimes the gait is uncertain, 

 inco-ordinated, and hesitant ; at others the animal shows lameness or 

 loss of control over a front or hind limb, or over two limbs simul- 

 taneously (either the two front or hind limbs or the diagonal limbs), 

 or it may be absolutely unable to stand. 



It walks obliquely, or the front or hind limbs collapse ; or again, 

 it may persistently lie down, a fact which makes the shepherd think it 

 is suffering from paralysis. On examination, however, no true indications 

 of paralysis can be found ; sensation and motor power are both pre- 

 served in a modified form. 



Death is very frequent at this stage of the disease ; the animals 

 eat little or nothing, re- 

 fuse drink, and die of ex- 

 haustion. 



All this general distur- 

 bance is of central origin, 

 and is due to disseminated 

 parasitic encephalitis, but 

 up to this point the seat ^^^ 2i8._Brain of a lamb infested with young 

 of the disease is not yet gidU-Addevworms {Ccenumscerebralis). Natural 



clearly apparent. size. (After Leuckart.) 



Second phase. — Tani- 

 skk. — -The central symptoms are slow of development, and are due 

 to the progressive growth of one or two, more rarely three or four, fer- 

 tile vesicles. These are the true symptoms of turn-sick, and it is only 

 after this phase of the disease has developed that the term becomes 

 appropriate. 



Left at liberty, the patient usually walks in a circle towards the right 

 or left in an impulsive and irresponsible fashion. Sometimes it describes 

 a circle, always of the same size. In other cases, on the contrary, it 

 travels along a spiral track, getting further from or nearer to the centre 

 as the case may be. The turning movement may become so accentuated 

 that the animal appears to revolve as on a pivot, and if it is confined in 

 a field or straw-yard its legs become caught in the litter and it falls to 

 the ground. 



Attempts have been made under these circumstances to discover the 

 exact point of compression, i.e., the point at which the cyst exists, by 

 noting the direction of the turning movement. The diagnosis, however 

 arrived at in this way is frequently illusory, because it is not uncommon 



