APPENDIX G: JENNER 429 



which was on the eighth day after she received the infection, I found 

 her affected with general lassitude, shiverings, alternating with heat, 

 coldness of the extremities, and a quick and irregular pulse. These 

 symptoms were preceded by a pain in the axilla. On her hand was 

 one large pustulous sore. 



It is curious also to observe, that the virus, which with respect to its 

 effects is undetermined and uncertain previously to it passing from the 

 horse through the medium of the cow, should then not only become 

 more active, but should invariably and completely possess those spe- 

 cific properties which induce in the human constitution symptoms sim- 

 ilar to those of the variolous fever, and effect in it that peculiar change 

 which forever renders it unsusceptible of the variolous contagion. 



May it not then be reasonably conjectured, that the source of the 

 Small Pox is morbid matter of a peculiar kind, generated by a disease 

 in the horse, and that accidental circumstances may have again and 

 again arisen, still working new changes upon it, until it has ac- 

 quired the contagious and malignant form under which we now com- 

 monly see it making its devastations amongst us? And, from a 

 consideration of the change which the infectious matter undergoes 

 from producing a disease on the cow, may we not conceive that many 

 contagious diseases, now prevalent amongst us, may owe their present 

 appearance not to a simple, but to a compound origin ? For example, 

 is it difficult to imagine that the measles, the scarlet fever, and the 

 ulcerous sore throat with a spotted skin, have all sprung from the 

 same source, assuming some variety in their forms according to the 

 nature of their new combinations? The same question will apply 

 respecting the origin of many other contagious diseases, which bear 

 a strong analogy to each other. 



H. PRINCIPLES OF GEOLOGY : BEING AN ATTEMPT TO EXPLAIN 

 THE FORMER CHANGES OF THE EARTH'S SURFACE BY 

 REFERENCE TO CAUSES NOW IN OPERATION 



BY CHARLES LYELL, ESQ., F.R.S. 



[The first edition of this epoch-making work appeared in 1830 and the second 

 edition, from which the following excerpts are taken, in 1882. Few if any books 

 of the nineteenth century have had greater influence upon human thought. The 

 first four chapters constitute an invaluable review of previous geological opinion, 

 from the earliest times. The following quotations are from the end of the 

 fourth and the latter part of the fifth chapters.] 



