38o THE BIOLOGY OF BIRDS 



in any way. The only deleterious symptom was that the 

 proportion of fertile eggs in the matings of alcoholised parents 

 was below the normal. This last fact suggests that alcohol 

 and similar substances act as eliminative agents upon the 

 germ-cells of the treated animals, probably discriminating 

 between different types of ova or spermatozoa. 



The mortality among the treated hens was much smaller 

 than among the untreated control sisters. Neither the total 

 amount of egg production nor its distribution was signifi- 

 cantly different in the two sets of birds. Both the treated 

 birds and the controls laid normally and well. 



It must be noted that the number of birds used was small, 

 but subsequent experiments were made. It may also be 

 that the " treating " was too moderate to be of bodily 

 importance to the individual. 



According to O. Riddle and G. C. Basset (1916) a pro- 

 longed treatment of hens with alcohol by the inhalation 

 method reduces the size of the yolk, and the effect persists for 

 weeks or months. 



Numerous experiments have been made by A. Magnan 

 (1914) on the mechanical and chemical effects of different 

 diets on young ducks of the same brood. The naturally 

 omnivorous birds were able to thrive on insects or fish, on 

 flesh or vegetables. It was found that a vegetable diet 

 considerably increased the surface of the digestive canal, 

 while a flesh diet reduced it. The caeca and the short large 

 intestine were most developed in the vegetarians. The 

 weight of the intestine increased in those fed on hard food 

 and fish, for the muscular wall increased in thickness. This 

 was particularly noticeable in the case of fish-fed ducks, 

 though the intestinal wall was not the largest. The weight 

 and surface of the proventriculus increased in proportion 

 to the size of the prey. This is a purely mechanical effect 

 and was well-marked in the fish-eaters. 



Some chemical effects of the modified diet were also 

 observed, notably in the liver. Fish-diet and insect-diet 

 caused hypertrophy, but a pure flesh-diet and a pure 

 vegetable-diet both caused a reduction in the w^eight of the 



