CAUSATION. 387 



indicative that its true source is to be looked for in causes 

 dietetic ; also tliat, although green food of various kinds may 

 under certain conditions be provocative of various diseases, 

 and amongst these of diseases associated with the nervous 

 system, yet this special nervous disturbance is only induced 

 by feeding upon rye-grass, and that, too, at a particular stage 

 of its growth, and when the plant has either developed 

 within itself, or possesses the power of developing when taken 

 into the animal sj^stem, a specific disease-producing agent. 

 The idea which attributed this, as well as many other some- 

 what obscure abnormal conditions, to atmospheric influences 

 is sufficiently answered when it is known that the disease may 

 be eradicated by removal of the particular food-material we 

 consider the true inducing factor, when, to all appearances, 

 atmospheric and other influences remain as before. 



The particular period when the grass seems likely to induce 

 this disturbed innervation is when, the flower having been 

 developed, the stem becomes somewhat dry and hard-looking, 

 and the seed is being matured. Some have thought that it 

 was through a process of fermentation after the grass had 

 been cut that the poisonous element was developed ; this, 

 however, cannot be, seeing it operates in conditions where 

 fermentation could not possibly have existed — it produces 

 effects when the plants are eaten while grown in the fields as 

 well as when cut. Lambs are sometimes sufferers from this 

 condition, rarely or never their dams. The probable reason of 

 this seems to yield another item of evidence corroborative of 

 the statement that it is the grass when in the transition stage 

 which is the cause of the disturbance. That the ewes and 

 older sheep are not sufferers while grazing on the same 

 pastures where their lambs may be affected, seems capable of 

 explanation b}^ knowing that sheep do not incline to feed on 

 the tall seed-stems, but rather on the more lowly-growing and 

 succulent plant-leaves ; lambs, however, not confined to the 

 grass entirel}^ for their food, are disposed, more in play than 

 with the object of obtaining so much food, to nip off the tops 

 of the seed-stems of the rye-grass; this I have repeatedly 

 watched them doing. 



c. Anatomical Characters. — Opportunities to make after- 

 death examination in cases of enzootic paraplegia are not 



25—2 



