YELLOW FEVER. 429 



animals affected to the same cause. In advance of any 

 experiments designed to test the truth of such a deduc- 

 tion, it seemed quite improbable, from the fact that the 

 supposed effect only results exceptionally, if at all, while 

 domestic animals are frequently exposed in large num- 

 bers, in localities visited by severe epidemics of yellow 

 fever, without exhibiting any symptoms of sickness. 

 This fact is vouched for by many competent observers, 

 and is verified by the personal experience of two mem- 

 bers of this Commission. 



" Nevertheless, in view of the reports referred to, of 

 the great importance in the prosecution of the investi- 

 gation of a test of the presence of the poison, and of 

 the possibility that by close observation and the use of 

 the clinical thermometer some symptoms heretofore 

 overlooked might be discovered sufficient to serve as 

 such a test, it was evidently imperative that experiments 

 should be tried in this direction. Arrangements were 

 accordingly made before leaving New York for a supply 

 of animals as required, and on the 24th of July the 

 following were received, per steamer ' Niagara,' viz. : 

 Four dogs, two cats, six rabbits, six guinea-pigs, one 

 monkey, six chickens, twelve pigeons, and two geese. 

 Subsequently (August 30) six more dogs were received. 



" All of these animals were carefully observed, and 

 various experiments were tried for the purpose of test- 

 ing their susceptibility to the influence of the yellow 

 fever poison. The details of these experiments are 

 given in a special report to the National Board of Health, 

 dated October 15. It is not deemed necessary to give 

 these details in the present report, but the general state- 

 ment may be made that the results were negative. No 

 symptoms were produced in any of the animals experi- 

 mented upon which can fairly be attributed to the 

 influence of the yellow fever poison. 



