248 UNKNO WN CA USES OF OTHER INFECTIO US DISEASES. 



it will be readily seen, is only approximate. The treatment 

 is begun with an emulsion of the cords of the 14th and 13th 

 days of drying. On the second day the treatment is made 

 up of the cords of the 12th and llth days of drying; on the 

 third day, of the 10th and 9th ; on the fourth, of the 8th and 

 7th ; and on the fifth, of the cord which has been drying six 

 days. Thus the virulence of the injection is increased until 

 the third-day cord is reached, when we must revert back to 

 the fifth, and then fourth, both for two days, finally winding 

 up the treatment with the third-day cord. The above method, 

 as practised in the Pasteur Institute, is used for ordinary cases, 

 and consumes^about fifteen days. In severe cases two separate 

 treatments are given on each of the first three days, the sixth- 

 day cord being reached in the second injection of the third 

 day, and the treatment, which in other particulars is the same, 

 is continued for eighteen to twenty -one days. The depth of a 

 bite from a mad dog is supposed to influence the severity of its 

 effects. Bites about the face, head, and upper extremities are 

 considered more dangerous than those of the lower extremities. 



YELLOW FEVER. 



While much has been said and written about yellow fever, 

 nothing is definitely known about its cause except that the 

 Stegomyia calopus orfasciata acts as a carrier of the infection. 

 It is a delicate, dark gray mosquito, with lyre-shaped mark- 

 ings on its thorax. It has white spotting and striping on its 

 abdomen, but none on its wings. Its third pair of legs are 

 marked with bands. 



The blood of a yellow fever patient is capable of transmitting 

 the disease only during the first three days of the disease. 

 During this time the American Commission in Cuba showed 

 as little as 0.1 c.c. of infected serum was capable of reproducing 

 infection if injected directly into a non-immune. For infection 

 to take place by the bite of a mosquito, it is necessary that the 

 mosquito should have sucked the blood of a yellow fever patient 

 during the first four or five days, and that at least twelve days 

 shall have elapsed between that time and the time of biting a 

 non-immune. As only the female stegomyia is capable of trans- 



