FIG. 19. A DRAWING OF A SAWN SECTION OF THE VERTEBRA, at the region of the occurrence of the osteoma, showing how the pathological structure grew out of the body of the vertebra.

FIG. 20.

TIBIA AND FIBULA WITH TARSAL BONES OF Limnocyon potens, a carnivore from the Washakie Eocene, showing in the carious roughening and hyperostoses evidences of disease resembling the results of osteomalacia of today. Published through courtesy of Dr. W. D. Matthew.

bones, were persistent as may be seen in cases of caries and alveolar osteitis with the associated forms of necrosis. It is to be expected that the paleontological evidences of disease would be rather scanty during the Eocene and in fact not a great deal is known. One interesting indication of a pathological condition may be seen in the tibia, fibula and associated tarsal bones of Limnocyon potens, a creodont carnivore from the

Washakie Eocene. These bones (Fig. 20) show considerable exostoses and hypertrophy indicating an infection of some duration. The appearance of the bones suggests modern conditions of nutritional disturbances resulting in the softening and lightening of the bones as in osteomalacia.

OLIGOCENE

The mammals of the Oligocene suffered from disease and injury, though not so greatly as their successors, nor were any of the diseases prevalent at that time of sufficient importance to produce extinction. It must be remembered, however, that paleontological evidences of the antiquity of disease deal with hard parts exclusively, the soft parts known not being pathologic. The Oligocene dog, Daphænus felinus, so carefully and beautifully described and figured by Hatchers presents on the inferior portion of both radii a symmetrical tumor-like mass, the only example of duplicate exostoses in fossil animals. The nature of the exostosis is problematical and I have not been able to find a parallel for this condition among the lesions on human bones. An excellent example of fracture with resulting callus formation and a splendid pseudarthrosis is known in a rib of the right side of Titanotherium robustum a perissodactyl from the White River beds of South Dakota, described by Osborn. A careful account of this interesting fracture has been given by the writer, accompanied by a detailed illustration of the callus.

MIOCENE

As an example of the nature of disease during the Miocene may be mentioned the nature of the lower jaw of the type skeleton of Merychippus campestris, a three-toed horse from the Loup Fork beds of South Dakota. One ramus of the jaw has a prominent swelling indicating the presence of a long-standing infection possibly of actinomycosis in its early stages, before the eruption of the bone took place. Alveolar osteitis with the the upper right hand spine. k, end view of vertebra of saber tooth from the same beds, showing on the ventral surface of the body of the vertebra pathologic lesions of spondylitis deformans. Doubtless a series of vertebrae were ankylosed by the lesion, since the part shown is broken square across. Lesions of spondylitis deformans are fairly common in the mammalian remains of the Pleistocene.

6"Oligocene Canidæ," Mem. Carnegie Museum, Vol. 1, no. 2, p. 85, pl. XIX., figs. 9 and 11.

Bull. Amer. Mus. Natl. Hist., Vol. VII., p. 347, 1895.

8 Annals of Medical History, Vol. I, No. 4, 1918.

formation of some osteophytes, resembling the results of pyorrhea are also seen, and one molar tooth is afflicted with caries, a common occurrence among fossil animals.

PLIOCENE, PLEISTOCENE AND RECENT

The pathological conditions found among the mammals of the Pliocene, Pleistocene and Recent geological periods were the first known and have been extensively described and studied by a number of writers from Esper (1774) to Virchow (1895). There are about twenty contributions dealing with the diseased nature of bones from these periods. A review of our knowledge, especially of the pathology of fossil man, has been given elsewhere and little need be said here concerning the pathological evidences from these periods. A few examples of diseased and injured bones from the Pleistocene, Rancho la Brea beds of southern California shown in Fig. 21, a-k, will give an idea of the prevalence of disease in the bones from these periods.

SUMMARY

The above brief summary of paleontological evidences shows that in each geological period there are a few evidences of pathological processes known, although there has been no organized search made for diseased remains. In fact paleontologists as a rule have paid very little attention to evidences of pathology in fossil remains, though the subject is one which yields much that is interesting. The subject increases our vision as to the possibilities of medical history and extends our knowledge of the occurrence of disease back into geological time for many millions of years. No new ideas of pathology have been seen in the study of these ancient lesions-nor were any expected. Since the organization of animal and plant forms of ancient times differ in minute details only from those of recent times there is no reason why we should expect any new ideas. Doubtless many of the lesions described and figured above will on closer examination prove to be lesions of extinct diseases. We know from medieval history that diseases do become extinct and doubtless many of the diseases from which ancient animals suffered are now extinct. Their results, however, as seen in the fossilized bones, closely parallel the pathological anatomy of recent times.

9"Studies in Paleopathology. II., Pathological Evidences of Disease among Ancient Races of Man and Extinct Animals," Surgery, Gynecology and Obstetrics, 1918, figs. 1-45.

The question of extinction is still an open problem. A study of the paleontological evidences of disease, as seen in the bone lesions, does not help us much yet in an appreciation of what part disease may have played in extinction. The part may have been great, but this is a hypothetical assumption, based purely on analogy.

The subject of paleopathology and the significance of its study were first commented upon and developed by Sir Marc Armand Ruffer, while studying the lesions seen in Egyptian mummies. A study of fossil lesions is merely an extension of the work began by him but it broadens perceptibly the scope and value of paleopathology.