FOREST, FISH AND GAME COMMISSIONER. 1 55 



against certain enemies it reduces their defense against certain others, and 

 these are the bacteria and microscopic animal parasites. One may, more- 

 over, cite a specific way in which this reduction of resisting powers is brought 

 about. This is the anemia of domestication or lowering of the red coloring 

 matter of the blood, as shown by estimation of the hemoglobin. Repre- 

 senting the normal red color of healthy human blood by ioo, the average 

 of thirty-five wild brook trout examined was found to be 43.7, and of wild 

 rainbow trout from only two specimens, 92. Healthy domesticated trout 

 of the same species average considerably lower, the brook about 35, 

 the rainbow 54. In other words, domesticated brook and rainbow trout 

 have poorer blood than the corresponding wild trout, and it is probable that 

 the assertion applies to any trout, and in greater or less degree to most 

 species of fish the subject of domestication. It may not be the mere falling 

 off of hemoglobin which is immediately and alone responsible for attacks 

 of disease ; but it is well recognized that a high hemoglobin content favors 

 immunity from the infectious diseases, and that a lessening of hemoglobin, 

 causing anemia, is a lessening of bodily vigor. The hemoglobin of the blood 

 is the oxygen carrier and interference with it is an interference with an 

 essential life process. 



Taking domestication in a more specific way and considering the sepa- 

 rate conditions named to which bred trout are subjected, it is not always 

 easy to see just wherein these operate to the disadvantage of the trout, 

 save on the score that they are a departure from the natural conditions. 

 Artificial food varies only within narrow limits and is of a sort that trout 

 rarely or never get in their natural waters. While it meets the necessities 

 of a readily available nourishing food, acceptable to trout, fish culturists will 

 probably agree that a ration of natural living food, of various sorts, could 

 it be supplied in quantity would be preferable. To a certain extent domesti- 

 cated trout are deprived of the natural exercise which the mere capture of 

 living food affords, and this, added to the narrow range permitted by the 

 necessarily small size of preserves, must deprive them of an important 

 muscular function and the reaction which comes from its exercise. 



The third factor specified, crowding, is perhaps the most important of 

 all and is the common and necessary evil incidental to any form of domesti- 

 cation in which a large quantity of product is the object. The maximum 



