52 PLANT DISEASE 



ammonium sulphide ; the exact amount appears 

 to vary largely, but the causes of the variation 

 have not been determined." 



Can there be any question that the variation 

 in the quantity of iron found in the hepatic 

 substance varies according to the quantity of 

 iron in the haemoglobin which again varies as 

 the iron in the food eaten ? 



But of all forms of variation perhaps the 

 various degenerations of protoplasm are the 

 most to the point in this connexion. 



" The healthy appearance of the most 

 elementary kind of protoplasm is a soft trans- 

 lucent grey ; under the microscope this greyish 

 protoplasm is uniformly and finely granular. 



From this standard of health there are 

 various deviations, representing various kinds 

 and degrees of degeneration. The chief degene- 

 rations are the mucous, the albuminous, the 

 fatty, the calcareous, the caseous, and the 

 amyloid. Under the head of caseous are collec- 

 tions of pus, as in chronic abscess of the liver, 

 or pus in the pleural cavity, which are liable to 

 the same process of drying up and molecular 



