YELLOW FEFER 367 



Diluted blood passed through a Fasteur-Chambeiiand filter will 

 cause the disease when injected intravenously into a non-immune. 

 Time is recjuired for the virus to develop in man and the mosquito 

 before it is infective, three days in man and twelve days in the 

 moscj[uito, hence it cannot be a chemical substance. 

 If infected serum is diluted the virus becomes more and not less 

 potent after time has been allo^ved for growth. 

 The virulence of the blood is destroyed at 55° C. 

 The S. calopus is absolutely necessary for its spread. 

 Contact with the bedding, fomites and excretions of an infected 

 person will not cause it. The virus may only live in man and the 

 S. calopus. 



The higher apes, guinea-pigs and fowls are suspected. 

 The fly must go twelve days after feeding upon an infected patient 

 before its bite will reproduce the disease in man, but these flies are then 

 infective for life. 



According to French physicians the virus can be transmitted by 

 the mosquito to the first and second generations. These cannot infect 

 man until they have been adult flies for thirteen days. 



The adult mosquito can live for about five months and la}s seven 

 batches of eggs. The fly, before her first egg-laving, is immature and 

 bites at any time but is harmless. Afterw^ards she is strictly nocturnal. 



PATHOLOGY. 



The Liver. — The liver cells swell, pressing upon the bile capil- 

 laries obstructing the bile, causing hepatogenous jaundice, staining 

 the skin and tissues yellow and passing out in the urine. 



The swollen liver cells also block the intralobular capillaries causing 

 congestion of all viscera drained by the portal vein, especially the 

 pyloric region and the duodenum. This impaired circulation predis- 

 poses to secondary infection. 



Portions of liver are so degenerate that the urea function is impaired 

 and a universal toxic condition due to the resulting ammonic-emia sets 

 in. Haemorrhages are caused as a result of the damaged epithelial 

 lining of the capillaries. 



The Blood. — A few normoblasts may be present, otherwise the 

 number and shape of the red cells are normal. The loss of hb. is 

 marked after the third or fourth dav. The specific gravity of the blood 

 falls, its coagulation is diminished. 



Hasmoglobin^emia often occurs before death. 



Ammoniaemia is present in bad cases. 



The polymorphs are slightly increased, 3,200 to 20,000 per cm. 



The Urine. — Albumin on the second day which increases rapidly. 



