10 THE CONTAGIOUS TYPHUS 



So long as the herbivorous or grass-eating 

 animal is properly fed; so long as he browses 

 on fat pastures ; so long as his blood retains 

 those physiological elements which are the 

 prime condition of health, he can, and 

 does, resist the causes of most contagious 

 maladies. But if a hot summer and a long 

 continuance of dry weather chance to curtail, 

 in temperate zones, the usual abundance of 

 his fodder, then comes the fatal change : the 

 blood is impoverished, the secretions are de- 

 bilitated, a strange languor runs through the 

 system, the vital resistance is unnerved, and he 

 becomes an easy prey to those noxious in- 

 fluences which were encountered before without 

 injury whilst his provision was abundant. 



This is a fundamental matter. We there- 

 fore beg leave to support and justify our 

 argument by borrowing some additional evi- 

 dence from prior labours of ours, accomplished 

 at the Ecole d'Alfort, near Paris, conjointly 

 with Professor Delafond, whose name has so 

 often been cited in the public journals in 

 connexion with the cattle plague. 



All vegetables and animals, with the excep- 

 tion of adult men, whenever their health de- 



