No. 631] CO? 



-pigs 147 



when excited they run in a stumbling fashion and finally 

 the legs stiffen out and the animal falls on its side. This 

 affection is, however, not heritable, but has been demon- 

 strated by these investigators to be due to nutritional 

 disturbance, caused by a diet consisting too largely of 

 pampas grass. 



When there is a liberal amount of grass the actual number of cases is 

 small. After a long continued drought when the fine grass supply is 

 short, the number of sick animals is large. The mortality varies con- 

 siderably, young sheep seeming to suffer most. 



Man. — Among the numerous confusing and complex 

 nervous disorders in man there are several with certain 

 similarities to congenital palsy of the guinea-pigs. We 

 have not attempted an exhaustive survey of this field, but 

 list a few of them with remarks on resemblances or dis- 

 similarities. In some cases it is difficult to tell whether 

 the descriptions refer to the same or different affections, 

 the synonymy not being clear. The comparison with con- 

 genital palsy is also often uncertain owing to the indef- 

 initeness of the descriptions of symptoms. No attempt 

 at completeness has been made in the matter of refer- 

 ences, citations being added merely for giving authority 

 for the statements made. 



Feeble-mindedness (Davenport, 1911), epilepsy (Dav- 

 enport, 1911; Davenport and Weeks, 1911; Weeks, 1915) 

 and some forms of insanity (Davenport, 1911) resemble 

 congenital palsy in being definitely recessive in inher- 

 itance, but show no close similarities in other symptoms. 



Paralysis agitans (Parkinson's disease). (Curschmann, 1915.) 

 Tremor of muscles. Appears late in life. 



Progresses in severity with course Constant trembling. 



Habitual tremor. (Curschmann, 1915: Dana, 1887.) 



