F. 8. BILLINGS. 
245 
surface of the scrotum of an ox, it led to the development of a 
variola on the place in question. Ceely reports cases which fully 
demonstrate the facility with which variolic contagium attaches 
itself to a delicate cutis: Ceely frequently applies vaccine to the 
cutis of children and young persons without having recourse to 
puncture and obtained positive results in that he applied the 
lymph directly to the cutis, and covered the same with a thin 
layer of blood, which soon dried and protected it from the action 
of the air. 
In opposition to my assumptions it may be asked, Why the 
hand of the milker is not first infected with the vaccine ? I can 
only answer, that in this direction the long-continued and fre¬ 
quently-repeated manipulations of milking fail as assistant causes; 
and on the other side the cases are not infrequent, where an 
infection of the hand or arm of the milkers is infected from the 
udder of the diseased milk-cow. Again, cases of accidental 
transference of humanized vaccine from man to man are now and 
again reported. Sacco reports of a 19-year-old servant-girl who 
attended two vaccinated children, and who had frequently to 
change the bandages of the suppurating pustules, that a 
pustule appeared on the eighth day upon the little finger, which 
took a regular course, and generated vaccine pustules on being 
inoculated to others. As the vaccine of the cow may be trans¬ 
mitted to milkers, so may the accidental transmission of human¬ 
ized vaccine from man to man take place. 
As a final reason, that the so-called genuine bovine variola 
comes to pass only by means of foreign infection, I must call 
attention to the fact, that the local eruption upon the udder 
almost always takes place gradually, from time to time, not 
coevially. In my opinion, this fact finds only one satisfactory 
explanation, viz: that from one or more variolse due to primary 
infection, secondary variolse are again developed by means of 
self-infection, which is very easy in consequence of the intimate 
relations which frequently take place between the stable floor or 
the bedding, or by means of the manipulations of milking. On 
the contrary, we see by human and ovine variola, where the 
organism is infected by the volatile contagium by the way of 
