508 PROCEEDINGS OF SECTION H. 



across the aperture to corresponding points on the opposite margin ; 

 while on the latter are written, in terms of a square inch, the 

 areas of circles having diameters equal to the imaginary lines. 

 This plate being laid on the skin, the cicatrix is seen through the 

 aperture ; and the point at which its cii'cumference touches both 

 the lateral margins of the aperture being found by moving the 

 plate up or down, its approximate area may be read off. Doubtless 

 the desirability of using some such appliance as this has suggested 

 itself to others ; and perhaps they may have been deterred by the 

 fear I myself felt, that it would prove too troublesome to be often 

 employed. This might well be the case if a nearly accurate 

 measurement were necessary ; but indeed this cannot be made, 

 since scars are most often not circular But all that it seems in- 

 dispensable to learn, if any such method be followed, is whether the 

 scarred surface is more or less than half an inch in area ; and this 

 may be easily and expeditiously reckoned with the gauge. I 

 propose, therefore, that the record should not be expressed in 

 terms of a square inch, but that scars should be described as 

 being of " sufficient" or of " deficient" area ; that is to say, as 

 having an area of more or less than half a square inch. 



This point then is arrived at :— That scars of primary vaccina- 

 tion may be classified first, by their good or bad character ; and 

 secondly, as being sufficient or deficient in area. Thus four 

 categories are formed, namely, area sufficient, character good ; 

 area deficient, character good ; area sufficient, character bad ; 

 area deficient, character bad. 



Note on Glassification hyAge. — It remains to classify the subjects 

 already arranged in the above four categories by age ; for liability 

 to post-vaccinal small-pox is greatest between the ages of fifteen 

 and twenty-five. Increased liability to post-vaccinal small-pox 

 begins to show itself at the age of ten years ; however, the 

 majority of attacks occur between the ages first named, and 

 therefore, each of these four groups must be sub-divided into 

 three : comprising, namely, those persons who are under fifteen, 

 those between fifteen and twenty-five, and those above the 

 latter age. 



PKOPOSITION III. 



Persons who allege re- vaccination should be classed as showing, 

 or as not showing scars ; secondarily as having been re- vaccinated 

 above or below the age of ten-years. 



Note on the Classification of Scars of re-vaccination. — Careful 

 observation causes me to assert that iii the matter of re- vaccination 

 the patient's verbal statement must be relied on ; or rather is the 

 only available source of information, speaking generally. The 



