YELLOW FEVER 509 
the Leptospirata in the blood. Successfully infected guinea-pigs 
usually die in about ten days. The organisms may be found in the 
tissues and lilood stream and urine, and there is characteristic jaundice, 
and subcutaneous hemorrhages especially about axillary and inguinal 
lymph glands. Examination of blood, urine and tissue films of these 
guinea-pigs by stains or dark-field illumination as above. 
4. Examination of urine for Leptospirata: The urine is centrifuged 
and the sediment examined by the dark-field illumination, or by 
suitable staining methods. Urine may contain spiral organisms other 
than Leptospira icterohaemorrhagiae; hence, much caution must be 
observed in arriving at a diagnosis. Carriers may be detected by 
urinary examination. 
5. Urine may be injected into guinea-pigs. The guinea-pig is the 
most reliable reagent for the detection of the organism. 
6. Tissues from autopsies, as fresh as possible, are examined by 
direct smear, by dark-field illumination and by maceration and injec- 
tion into guinea-pigs to establish a diagnosis. 
The examination of rats for Leptospira icterohsemorrhagiae does not 
differ materially from that of man, except that the animal is killed, 
and the kidney removed immediately with sterile precautions, macer- 
ated, and injected into guinea-pigs. Some of the maceration fluid is 
examined directly for the organisms. 
YELLOW FEVER. 
Yellow fever^ is an acute fever of tropical and subtropical countries, 
characterized by jaundice, albuminuria and a tendency to hemorrhage 
from mucous membranes; the latter is especially marked in the stomach 
and the "black vomit" which occurs frequently is a regurgitation of 
altered blood which has collected in the stomach. 
For many years the etiology and mode of transmission of yellow 
fever were wholly unknown, although many and divers organisms 
were reported as the inciting factor. Finlay,- as early as 1882, believed 
that mosquitoes played an important part in the transmission of the 
disease and he actually attempted to infect non-immunes by mos- 
quitoes which had previously bitten yellow fever patients. His 
experiments were wholly negative, partly because the extrinsic cycle 
of development in the insect was unknowai. Carter^ made the very 
important observation that a latent period of about two weeks elapses 
between primary and secondary cases of yellow fever. This discovery 
explained some of Finlay's negative results and paved the way for the 
success of the American Yellow Fever Commission. Finally Reed, 
Carroll, Agramonte and Lazear,^ a commission appointed from the 
> See Leptospira icteroides, page 601. ^ jour. Am. Med. Assn., 1901, 37, 1387. 
3 Public Health Report, 1905, 20, 1350; New York Med. Rec, 1906, 69, 683; New 
Orleans Med. Jour., May and June, 1900. 
4 Jour. Exp. Med., 1900, 5, 215; Am. Public Health Assn., 1900, 26, 37; Boston Med. 
and Surg. Jour., 1901, No. 14; Jour. Am. Med. Assn., 1901, 36, 413; Senate Document 
No. 822, January 27, 1911. 
