6 
I have put on one Stock the leading Exanthems, or Fevers which 
are invariably accompanied by a decided eruption on the skin. The oldest 
in history of this group is Small Pox. Mr. Moore has shown that this disease 
was known in China and Hindostan a thousand years before the Christian Era, 
but it is not alluded to by any of the Greek or Eoman writers. It was 
introduced into Europe in 569, the year of the birth of Mohammed, it then 
swept at intervals like a plague over Europe and at a later period over the 
new world until the sublime discovery of Jenner checked its ravages, and 
that discovery having been only partially utilized on account of the 
ignorance of human nature, the disease again threatens to re-assume its 
former vigour. To prove its affinity to the rest of the group I may 
mention that all the early writers in the seventh and eighth centuries, 
such as the Arabian writers Ehazes and Avicenna, confound the disease 
with Measles ; they accurately and graphically describe the characters of 
each disease, but consider them only modifications of the same affection ; 
they did nothing towards preventing their spread, believing with many 
modern Sanitarians that these diseases are simply the result of putrefaction 
of animal and vegetable matter and not the result of infection from person 
to person, a doctrine which even now presents the most formidable obstacle 
to the adoption of true preventive measures. 
Dr. Darwin, whose work on the origin of species in animals suggested to 
me the somewhat bold idea of applying his hypothesis of evolution to these 
diseases, states that where different species have arisen from the same 
common prototype, their resemblance to the common type and therefore 
to one another is greater during the early stages of development. This 
applies to Small Pox when compared with other members of the group. 
The early eruption of Small Pox is frequently so precisely similar to that 
of Measles, especially when it appears first on the arms, that I have been 
unable te give a definite opinion for 24 hours. The general symptoms are 
much alike, but as either disease advances the diagnostic symptoms become 
more pronounced and unmistakeable. Time would fail me to mention in 
detail other resemblances, but they are such as to induce me to belieA-e 
that these two diseases, in the unknown past of our race, came from a 
common origin. Of their absolute origin in time and the mode of that 
origin science and history as yet know nothing definitely. 
Again, take Scarlet Fever and Measles, now known to be distinct species, 
each having as definite a history as any animal or plant, although the 
history of Scarlet Fever does not extend beyond two centuries. This 
disease, probably imported from Italy, made its appearance in London in 
