Chap. XXV. CORRELATED VARIABILITY. 331 



iinctoria. According to Spinola and others,*^ buckwlieat {Poly- 

 gonum fagopyrum), when in flower, is highly injurious to white 

 or white-spotted pigs, if thej are exposed to the heat of the 

 sun, but is quite innocuous to black pigs. According to two 

 accounts, the Hypericum crispum in Sicily is poisonous to white 

 sheep alone ; their heads swell, their wool falls off, and they 

 often die ; but this plant, according to Lecce, is poisonous 

 only when it grows in swamps ; nor is this improbable, as 

 we know how readily the poisonous principle in plants is 

 influenced by the conditions under which they grow. 



Three accounts have been published in Eastern Prussia, of 

 w^hite and white- sjxjtted horses being greatly injured by 

 eating mildewed and honeyde wed vetches ; ever}^ spot of skin 

 bearing white hairs becoming inflamed and gangrenous. The 

 Rev. J. Eodwell informs me that his father turned out about 

 fifteen cart-horses into a field of tares which in parts swarmed 

 with black aphides, and which no doubt were hone^^le wed, and 

 probably mildewed; the horses, with two excej)tions, were 

 chestnuts and bays with white marks on their faces and 

 pasterns, and the white parts alone swelled and became angry 

 scabs. The two bay horses with no white marks entirely 

 escaped all injury. In. Guernsey, when horses eat fool's 

 parsley (JEthusa cynapium) they are sometimes violently 

 purged ; and this plant " has a peculiar effect on the nose 

 ■■' and lips, causing deep cracks and ulcers, particularly on 

 *' horses with white muzzles."*^ With cattle, independently 

 of the action of any poison, cases have been published by 

 Youatt and Erdt of cutaneous diseases with much consti- 

 tutional dnsturbance (in one instance after exposure to a hot 

 sun) affecting every single point which bore a white hair, but 

 completely passing over ^ther parts of the body. Similar 

 cases have been observed with horses.*^ 



*^ This fact and the followiug cases, eating buckwheat; whilst black or 



when not stated to the contrary, are dark-woolled individuals are not in 



taken from a very curious paper by the least affected. 

 Prof. Heusinger, in ' Wochenschrift ^^ I\Ir. Mogford, in the ' Veteri- 



fiir Heilkunde,' May, 1846, s. 277. narian,' quoted in 'The Field,' Jan. 



Settegast (; Die Thierzucht,' 1868, }). 22, 18G1, p. 545. 

 39) says that white or white-spotted *^ ' Edinburgh Veterinary Journal,' 



sheep suiier like pigs, or even die from Oct. 1860, p. 347. 



