554 



In view of these remarkable facts 1 have drawn separate charts for 

 each of the 13 years (1880 to 1892) referred to in the preceding paragraph 

 and have appended them to this paper for the benefit of members who are 

 particulary interested in the subject; but their construction being different 

 from other charts of this kind, 1 beg leave to explain briefly the plan on 

 which they have been drawn. 



Bearing in mind that yellow-fever patients infected in the last 4 days 

 of a given calendar month, as a rule, are only taken sick or reported in the 

 following, and my purpose being to show the mean temperatures of 'lays 

 of possible infection, 1 have included in each column corresponding to the 

 yellow fever invasions recorded at the Military Hospital in a given month 

 the mean temperatures of the last 4 days of the preceding month, omitting 

 on the order hand those of the 4 last days of the calendar month under 

 consideration. Moreover the mean temperatures are not tabulated in their 

 order of succession but merely distributed so as to show in each column 

 the number of days which have shown a certain degree (centigrade) 

 including all decimals between it and the next degree above. 



These charts clearly show the close relation which formely existed in 

 Havana between the number of days of possible infection which had 

 presented mean temperatures favourable for the functional activity of the 

 stegoinyia calopus and the number of yellow fever invasions recorded at 

 the Military hospital. 



The three hottest years of the series (1880, 1882 and 1883,) were the 

 only ones in which upwards of one thousand yellow fever invasions were 

 recorded at the Military hospital). And, in each individual year, the 

 calendar month in which the greatest number of yellow fever invasions had 

 occurred proved almost invariably to have been the one in which the days of 

 possible infection with mean temperatures 27° and 31° C. had been most 

 numerous. 



On the other hand, the year 1886 which showed lower mean 

 temperatures than any other in the series, was at the same time remarkable 

 for the small number of yellow fever invasions during the first five months 

 of that year; an event which could only be attributed to the low mean 

 temperatures recorded in January and February, leading to an almost 

 complete extinction of the infection from purely natural causes. 



One of my objects in publishing these data has been to solicit similar 

 ones from other yellow fever centers, so that it may be known to what 

 extent the stegomyia calopus is able to accomodate itself to different 

 temperature conditions under the influence of climatic variations. Indeed 

 I cannot but attach considerable importance to the study of the habits 

 of the stegomyias of other insects which are known to trasmit infectious 

 diseases, being of opinion that without such knowledge our means of control 

 must always be imperfect. 



