YELLOW FEVER 129 



the cases into simplex, mitior and gravior. The first 

 group he states may occur at any time in an epidemic, 

 but cases are more prevalent towards the close. This form 

 was first recognized in 1841, and previously had been 

 known as ephemeral fever, and in that form the mor- 

 tality was ////. In the mitior and gravior the mortality 

 was from 20 to 25 per cent., and the total mortality 

 amongst all recognized cases was 13*3 per cent. The 

 epidemic ceased, but was followed by widespread in- 

 fluenza, and amongst sailors cases continued to occur 

 presenting some of the yellow fever symptoms grafted 

 on intermittent fever. That at this period the very mild 

 form of some cases was clearly recognized is shown by 

 the application of the remark that it varied in intensity 

 from a " flea-bite to the plague." 



He, like all the older authorities, contended that the 

 cases of the disease amongst the negroes were milder, not, 

 as so many subsequent writers have stated, that the negro 

 was immune. 



In the next outbreak in 1853 he also subdivides the 

 cases according to race : 



Cases Deaths Per cent. 



Seamen ... ... ... ... 1,242 ... 328 ... 27 



E. Indians (natives of India) ... 42 ... n ... 26 



Madeira (Portuguese) ... ... 698 ... 246 ... 35 



Creoles 17 ... 2 ... n 



The actual case mortality not only varies in different 

 outbreaks, but is to a great extent dependent on the 

 recognition of the mild form simplex as those cases, 

 which in some outbreaks are numerous, have no mor- 

 tality, and consequently, unless they are included, the 

 mortality will appear higher than it really is. 



Clarke gives an account of the 1793 epidemic as it 

 affected the inhabitants of Dominica. The mortality was 

 high, especially among the immigrants, irrespective of 

 race, and he gives an instance of twenty-four negroes 

 from West Africa who were all attacked, and of whom 

 one-third died, indicating that at that time the West 

 9 



