WALTER REED. 553 



The personnel consisted of three nurses and nine nonimniinies, all 

 in the military service, and included tAvo ph3'sicians. 



From time to time Spanish immigrants, newl}^ arrived, were 

 brought in directly from the immigi\ant station; a person not known 

 to be immune was not allowed to leave camp, or if he did was for- 

 bidden to return. 



The most complete record was kept of the health of every man to 

 be experimented upon, thus eliminating the possibility of any other 

 disease than yellow fever complicating the case. 



The mosquitoes used w^ere specially bred from the eggs and kept in 

 a building screened by wire netting. When an insect was wanted for 

 an experiment it was taken into a yellow-fever hospital and allowed 

 to fill itself Avith the blood of a i^atient; afterwards at varying inter- 

 vals from the time of this meal of blood it was purposely applied to 

 nonimmunes in camp. 



In December five cases of the disease Avere dcA^eloped as the result of 

 such applications; in January, three, and in February, tAvo, making 

 in all ten, cxcIusIa e of the cases of Doctors Carroll and Lazear. Im- 

 mediatelv upon the appearance of the first recognized symptoms of 

 the disease, in anj^ one of these experimental cases, the patient was 

 taken from Camp Lazear to a yelloAv-fcA^er hospital, 1 mile distant. 

 EA'Cry person in camp Avas rigidly protected from accidental mos- 

 quito bites, and not in a single instance did yellow feA'er deA^elop in 

 the camp, except at the Avill of the experimenters. 



The experiments were conducted at a season Avhen there was the 

 least chance of naturalh' acquiring the disease, and the mosquitoes 

 used Avere kept active b}' maintaining them at a summer temperature, 



A completely mosquito-proof building was divided into tAvo com- 

 partments by a Avire screen partition; infected insects Avere liberated 

 on one side only. A braA'e nonimmune entered and remained long 

 enough to allow himself to be bitten scA^eral times. He Avas attacked 

 b}' yellow fcA'er, Avhile two susceptible men in the other compartment 

 did not acquire the disease, although sleeping there thirteen nights. 

 This demonstrates in the simplest and most certain manner that the 

 infectiousness of the building Avas due only to the presence of the 

 insects. 



Every attempt Avas made to infect individuals by means of bedding, 

 clothes, and other articles that had been used and soiled by patients 

 suffering Avitli virulent yelloAv fever. 



Volunteers slept in the room Avith and handled the most filthy 

 articles for tAventy nights, but not a symptom of yelloAV fever Avas 

 noted among them, nor was their health in the slightest degree 

 affected. Nevertheless they Avere not immune to the disease, for 

 some of them Avere afterAvards purposely infected by mosquito bites. 

 SM 1005 39 



