19 



TABLE VI Continued 



Material collected as it had dried in the field. Sheep quite sick. 



When animals are poisoned with the narrow-leaved milkweed they 

 are affected for a considerable time, the poison appearing to be elimi- 

 nated slowly. Because of this slow recovery it was thought that small 

 amounts fed daily might cause an accumulation of the poisonous prin- 

 ciple in the animal. 



Ewe 37 was fed daily 2 ounces of sun-dried milkweed for six days 

 without showing any symptoms of poisoning. The dose was then 

 increased to 3 ounces for two days. On the following day, 4 ounces 

 were fed without causing any symptoms, and two days later she was 

 fed 5 ounces and became only slightly sick. During the ten-day period 

 she had been fed a total of 27 ounces ; yet it was only on the last day, 

 when she was fed 5 ounces, that she showed any signs of poisoning. In 

 all the tests summarized in Table II the feedings of 5 ounces produced 

 symptoms of poisoning. These successive feeding tests of Table VI 

 indicate very clearly that there is little if any cumulative action when 

 the milkweed is fed at brief intervals. 



Sheep 59, which had been made very sick with 4 ounces in an earlier 

 experiment, was fed 2 ounces daily for two days ; then 4 ounces were 

 fed without producing any symptoms. Two days later, when again 

 fed 4 ounces, this animal was made slightly sick. This feeding test 

 also indicates that there is no cumulative action when small doses are 

 fed on consecutive days. 



Three days later, on November 3, Sheep 59, the same animal as 

 mentioned above, was fed 6 ounces of the sun-dried milkweed, which 

 made it quite sick. Five days later it was fed 7 ounces and again it 

 developed symptoms of poisoning. Finally, on November 12, four days 

 later, 7 ounces were fed, the animal again becoming slightly sick. Each 

 of these feedings made the animal sick, but not nearly so sick as the 

 original 4 ounces. The last three feedings were made with a different 

 lot of milkweed material which may have been less poisonous ; although 

 when 5 ounces of this lot was fed to another ewe it made her sick for 

 two days. 



Animal lOa died when given the second feeding of 2 ounces. This 

 case can hardly be considered as at all typical because the animal was 

 found to have a badly diseased kidney which may have retarded the 

 elimination of the poison and hastened death. 



Sheep 120, when fed the same amounts and in a similar way as 

 Sheep lOa, developed no poisoning symptoms and to all outward 

 appearances was normal. 



These tests prove rather clearly that there is no cumulative action of 

 the poisonous principle in sheep. The same, it is believed, will hold 

 true for other animals. Rather, they seem to show that there is a 



