COW-POX AND HUMAN VARIOLA — PREPARATION OF VACCINE. 669 

 COW-POX AND HUMAN VARIOLA — PREPARATION OF VACCINE. 



Time and experience having proved that inoculation with cow-pox 

 or vaccinia protected human beings against small-pox, the question 

 arose as to the connection between the two diseases, whether or not 

 they were identical and whether vaccinia in the bovine animal might 

 not merely represent an alternative form of small-pox. The importance 

 of the question will at once be understood by bearing in mind the 

 danger to which human beings would be exposed by vaccination with 

 small-j)Ox virus unmodified by passage through the calf. 



Nevertheless, at the present time the opinion of the early writers 

 appears to prevail, and the theory of identity is accepted by the great 

 majority of scientific men. The reason why experimenters in the 

 second group came to believe in duality is that the method of inocula- 

 tion chosen (by puncture) was not entirely reliable. The inoculations 

 proved too slight, and it is only after inoculation by scarification or 

 incision that typical eruptions can be reproduced in series. 



Preparation of vaccine. Whether cow-pox and small-pox are or 

 are not identical, the benefits resulting from vaccination are none 

 the less real, and it is to be hoped that vaccination and revaccina- 

 tion will soon be made obligatory in all countries. We should then no 

 longer have to deplore those epidemics of small-pox which periodically 

 cause consternation in large cities and colonies. 



The preparation of vaccine has been the subject of such minute 

 care in every country that neglect of vaccination is astonishing. The 

 material is obtained- from calves or cows. In France the vaccine is 

 prepared from animals of five to eight months old, free from disease. 

 The old system of inoculation by puncture has been completely 

 abandoned, the yield being insufficient, scarifications or incisions being 

 now employed. 



The animal is secured or, better still, laid down on a suitable table, 

 and is shaven over a sufficient surface. The inoculations are made on 

 the sides of the chest, over the thorax or elsewhere, but preferably over 

 the flank and thorax, as being most readily accessible. The region of 

 operation is rendered aseptic as far as possible, and scarified in lines 

 about 1 to 2 inches in length, the lines of one horizontal row alter- 

 nating with those in the next. It is imperative that the slight bleeding 

 which may result should entirely cease before inoculation is attempted. 



The scratches are inoculated with the purest vaccine obtainable, 

 preferably with glycerinated pulp which has been kept for six weeks 

 or two months. From the third day the lines of inoculation become 

 prominent, and an indurated longitudinal swelling, with all the charac- 

 teristics of a pustule, soon projects above the neighbouring portions 



