No. 631] CONGENITAL PALSY IN GUINEA-PIGS 143 



ditions in the guinea-pigs. Dr. Bunting is making a study 

 of this phase of the question, and reports that "thus far 

 the only anatomical difference between affected and nor- 

 mal animals of the same litter, that has been noted, lias 

 been a definite hypoplasia of the parathyroid tissue in the 

 abnormal animals." He will, however, report more fully 

 later. 



For the present, therefore, we must be content with the 

 statement that the congenital palsy is due to a factor mu- 

 tation, the cause of which is unknown ; nor do we under- 

 stand what its action is on the animal organism to pro- 

 duce the nervous symptoms described. 



Discussion 



A number of nervous defects are known in man and the 

 lower animals which have certain points of resemblance 

 to congenital palsy as it occurs in our guinea-pigs, but we 

 have been unable to find any condition which agrees 

 closely enough in details so that the two could be consid- 

 ered identical. A list of some of these follows, with brief 

 mention of resemblances and points of difference. 



Pigeon. — Tumbl'my in pigeons appears to be due to lack 

 of nervous control of the muscles and associated to some 

 extent with certain voluntary efforts. This is especially 

 noticeable in Parlor Tumblers, which turn hack somer- 

 saults when they attempt to fly. The condition is greatly 

 exaggerated by excitement. Further similarities are that 

 the tendency to tumble increases with age, to a certain 

 point at least, and that it behaves in a general way as a 

 recessive to normal flight, though the crossbreds are usu- 

 ally intermediate and there appears to be no sharp segre- 

 gation in F 2 . Tumbling, unlike congenital palsy, does 

 not seem to affect the legs particularly, and does not in- 

 terfere with normal life processes sufficiently to be lethal 

 if the birds are given adequate protection and care. 



The condition described by Riddle (1918) as ataxia in 

 pigeons would appear to correspond very closely in symp- 

 toms to the more pronounced cases in Parlor lumblers. 



