PROTOZOA AND FOOD-SUPPLY 305 



the value of such birds is greatly reduced, for they 

 become much emaciated, and have little nutritive 

 value. Fish furnish food to many persons and even 

 nations. Here, too, man is affected by Protozoa, for 

 the Myxosporidia are notorious parasites of fishes, 

 sometimes producing tumours or sores, and at other 

 times causing malnutrition, and thereby lessening 

 their value as food. Certain Microsporidia also affect 

 fish in a similar way. The problem of fish diseases 

 is one demanding more attention than it is receiving 

 at present, and many hitherto inexplicable deaths of 

 fish are probably due to protozoal parasites. This 

 has been our experience in recent outbreaks in 

 England among freshwater fish, such as dace, bream, 

 and salmon. The extermination of the barbel from 

 the south of England, though not nearly so impor- 

 tant as the outbreak in Germany, was due to a 

 Myxobolus, and destroyed a source of food valued by 

 the peasantry in the south. 



The cost of living in England is one of the most 

 serious problems that has to be faced. At the 

 present time, the cost of frozen meat in England is 

 almost what was paid for the freshly killed home 

 product a quarter of a century ago. The effect on 

 prices of the stoppage of the home-supply from a 

 very limited area, due to an outbreak of " foot and 

 mouth " disease (probably due to a minute Protozoon), 

 has been most marked. The failure of stock from a 

 great exporting country, such as the Argentine, has 

 dire effects on nations restricted in their home sup- 

 plies like Great Britain and Germany. Practically 

 all kinds of animals used for food in England to-day 



3Q 



