3§4 



Annals of Medical History 



The geological development of disease has 

 certain curious characteristics which parallel 

 facts in the evolution of animals and plants. 

 Huxley many years ago called attention 



geological antiquity a few can certainly be 

 called persistent or primitive types which 

 have remained the same since the close of 

 the Paleozoic. Other diseases arose and 



Fig. 7. The skeleton of an early Tertiary mammal, Titanotherium robustum, 

 from the White River Oligocene of South Dakota, as it is mounted in the American 

 Museum of Natural History. The fifth rib on the right side has been fractured 

 and has healed with a pseudarthrosis and considerable callus. The deta Is are 

 shown in the enlarged sketch in the lower right hand corner. One-sixteenth 

 natural size. (Courtesy of Dr. W. K. Gregory.) 



to certain persistent types of animals which 

 had existed almost unchanged from early 

 geological periods down to the present. 

 Among the known diseases (Figs. 9-12) of 



became extinct, but some of them have 

 retained the same characteristics, as seen 

 in the resulting changes of structure. 



According to present evidences, disease 



Fig. 8. Two views of the mandible of a three-toed horse, Merychippus campestris, from the Miocene, about 

 one and one-half million years old. The figures show in the absorbed alveolar margins patho ogical processes 

 simi'ar to alveolar pyorrhea of the present day. A left premolar shows evidences of car es, and the swelling in 

 the left ramus, so evident in the right-hand figure is indicat've of a fistula, possibly indicating the presence of 

 actinomycosis in the early stages. (Courtesy of Dr. W. D. Mathew) 



