590 COMPARATIVE MERITS OF VACCINATION. 
lymph on the other, so as to detect more exactly the difference 
of effect in these methods. He was enabled also by the 
epidemic of smallpox which spread through various parts of 
America during 1872-73, to ascertain the advantages of animal 
vaccination over the long-established arm-to-arm method. 
This leads us to our author's next query, ‘‘Does the practice 
of animal vaccination offer such advantages over that with 
long humanised virus, as to justify us in abandoning the 
latter and adopting the new method?" The reply is derived 
from a study of the duration of the disease and its regular 
progression through certain ^veil-defined stages, from no¬ 
ting the character of the vesicle and its crust, and from the 
appearance of the cicatrix remaining. In these respects the 
effects of both methods are described and compared. It is 
well to bear in mind that in studying vaccinia the same rule 
is applicable as holds good with other diseases, that the 
changes should be noted day after day , and that results 
grounded on observation of the vaccine vesicle, at intervals 
of say eight days, are not strictly correct. Dr. Martin 
observes this rule, and his results are as follow :—Vaccinia, 
according to the earlier writers on the subject, and as noted 
by Dr. Martin in children vaccinated with heifer-transmitted 
cowpox lymph, extends over twenty-one or even thirty-two 
days, reckoning from the insertion of the virus to the 
spontaneous fall of the crust. But with the use of long 
humanised lymph he observed a great diminution in duration 
—“ The course of the disease induced by this virus, (obtained 
from Mr Robert Ceely of Aylesbury in 1859, and later from 
the National Vaccination Institution of Great Britain) was 
usually eleven days from insertion till the crust fell; it was 
an unusual circumstance for a crust from this vaccination to 
adhere till the fourteenth day." Again, animal vaccinia 
pursued a definite course, papulation appearing at the end of 
the third or beginning of the fourth day, the areola commenc¬ 
ing at the latter end of the ninth or beginning of the tenth 
day, the formation of crust or scab being accomplished on 
the sixteenth or seventeenth day, and failing off spontaneously 
about the twenty-fifth. In children vaccinated with human¬ 
ised lymph the stages of vaccinia were of much shorter 
duration. These points are illustrated by a reprint, by the 
heliotype process, of M. ChazaTs illustrationsin M. Bousquet’s 
work, and though imperfect as a print, it shows well the 
characteristics of these two forms of vaccinia. The crust re¬ 
sulting from animal vaccinia approached very nearly the size 
of the vesicle, was of a rich dark brown, or dark mahogany 
colour, and employed for vaccinating children showed great 
