16 SMALL-POX AND VACCINATION. 



invite your very special attention to this other series of diagrams, 

 which exhibit in the most convincing and instructive manner, 

 the influence of vaccination in preventing and modifying that 

 disease under different conditions and periods of life. They 

 show the results, based upon a most painstaking and successful 

 investigation, of a thousand cases of small-pox, treated in hos- 

 pital during 1871, by Dr J. B. Eussell. The diagram, as you 

 observe, is divided into large squares, each being subdivided 

 into one hundred smaller squares, so that each large square 

 represents one hundred cases of small-pox. The colouring 

 again, whether black, red, or white, tells you the degree of 

 severity with which each case was affected. Those portions of 

 the squares in white, show how many were attacked with the 

 mildest, or seldom fatal form of the disease (with rare or sparse 

 eruption). Those in red indicate intermediate, or frequently fatal 

 conditions of the disease (copious eruption) ; while the black marks 

 the dangerous, or very fatal type of the malady (confluent erup- 

 tion). 



The upper row of squares, from left to right, shows the effects 

 of vaccination between the periods of infancy and adult life 

 when well done ; the corresponding middle row, its effects when 

 badly done ; and the lowest row, when not done at all. 



By glancing at the diagrams in this order, you will at once 

 observe, that the well- vaccinated, as they grow older, take the 

 disease in a slightly severer form ; the badly vaccinated in a 

 much more severe form ; and those who have not been vaccinated 

 at all, are throughout their whole lives from infancy upwards 

 subjected to the very worst and most fatal form of the disease. 

 In other words, you will not fail to draw the inevitable conclu- 

 sion, "that the influence of vaccination, well and thoroughly 

 done, extends, with but little loss of protecting power, through- 

 out life ; while, if badly or imperfectly done, it is never so effi- 

 cient a protective power, gradually loses what protecting power it 

 had possessed, and finally leaves the badly- vaccinated individual 



