enlargements among recent crinoid stems, as described and figured in the Reports of the Challenger Exploring Expedition, that these enlargements were due to the parasitic action of myzostomids. Graff supported his interpretation by describing the carbonized remains of some worm, supposedly one of the myzostomids, to which the tumor was due, preserved in a channel of one of the fossil lesions. Similar objects are common from the Carboniferous of North America and doubtless they have a very wide distribution.

During the Carboniferous also there was a widespread development of fungi and bacteria which doubtless were influential in the spread of disease. Renault has found these forms abundantly preserved in the fossilized feces of fishes, in ancient wood and in coal. He also discovered in the teeth of certain extinct fishes indications of caries, as shown by the irregular decayed spots within the substance of the teeth. Renault's work covered many geological periods later than the Coal Measures, and his large monograph is the summing up of twenty-four years of activity spent in investigating the nature of the "Microorganismes des combustibles fossiles" in peat, lignite, bituminous schists (in which he found rhizopods, bacteria and fungi), boghead coal, cannel, ancient schists and the silicification of organisms in very ancient rocks. Renault's work is of great importance. A few of his figures are given herewith (Figs. 1-6). The bacteria take the form of coccoids, bacilli, diplococcoids and micrococcoids. Often in sporangia of the early cryptogamous plants Renault found natural cultures (Fig. 5) of bacteria which have been preserved by silicification. These organisms, which have been made so well known by the studies of French scholars, may all of them have been non-pathogenic forms, but the possibility of their being the cause of the disease of succeeding forms of life is very evident, and they should be mentioned as possible sources of disease.

PERMIAN

The great Permian period, with its widespread development of curious reptilian forms, has furnished us with the first evidences of traumatic conditions as they prevailed among the early forms of life. Fractures may have occurred earlier than the Permian, but they have not yet been seen. The oldest known fractures are found among the reptiles from the Permian of Texas. A left radius of Dimetrodon, a primitive reptile, pre

FIG. 5. SILICIFICATION OF A NATURAL CULTURE OF BACTERIA FROM THE PERMIAN. FIG. 6. MYCELIA AND SPORANGIA OF FOSSIL FUNGI as seen under high magnification in a thin section of fossil wood. Favorite places for the growth of bacteria. All figures taken from Renault's monograph "Microorganismes des combustibles fossiles."

FIG. 7. LEFT RADIUS OF Dimetrodon, a primitive reptile from the Permian of Texas, showing, in the enlarged portion of the bene above, a simple fracture and considerable callus with some intermediary callus. Specimen the property of the Walker Museum University of Chicago. Loaned for study and description by Dr. S. W. Williston.

FIG. 8. X-RAY PICTURE OF THE BONE. The fracture lines above and below the callus are post-fossilization fractures and have no significance.

sents a well-marked case of fracture (Fig. 7) with subsequent healing, although there is still some intermediary callus. An attempt to study the nature of this fracture by means of the X-ray has not resulted in any new knowledge, but it may be interesting to present the attempt (Fig. 8). The fracture runs directly across the bone, as do all the early cases of fracture among animals with solid limb bones, and the resulting callus has produced a decided enlargement of the bone around the fracture. The fractures seen in the X-ray picture above and below the callus were produced after fossilization and have no significance.

A small fragment of a fractured rib from the same beds, in which there was quite an old callus, has been studied micro

scopically (Fig. 9). The callus was quite evidently an old one, for the fracture was completely healed. A study of the microscopic section proves this to be true, since evidences of osteosclerosis and osteohypertrophy are clearly evident. The region

FIG. 9. MICROSCOPIC STUDY OF THE DETAILS OF A FRACTURE IN A RIB OF A REPTILE FROM THE PERMIAN OF TEXAS. The white spicule running vertically in the figure is the ingrowth of bone into a split portion of the rib. On the left of this spicule is to be seen the osteosclerotic portion of the old callus, indicated by a heavy unorganized deposit of calcium carbonate or some similar salt. On the right is seen the hypertrophied area, identified by the heavy deposition of bone with small lacunae and canaliculi. The lacunae have largely disappeared in reproduction but are clearly evident on microscopic examination of the bone.

of the figure to the left of the spicule of bone is regarded as due to osteosclerosis, which is interpreted on the basis of the presence of a heavy deposit of calcium salts and the absence of osseous trabeculae. The white band running vertically may be interpreted as a spicule of bone due to the splitting of the rib. Its bony nature is definitely established by the presence of lacunae, and its presence in this position is due to the ingrowth of new bone along a cleft produced by the splitting of the rib. The hypertrophied area to the right of the osseous band is often seen in old calluses and is interpreted on the basis of the presence of numerous trabeculae of bone. There is no evidence that the fracture was infected, necrotic sinuses being entirely wanting.

TRIASSIC

Except for occasional specimens of fossil fishes and other forms preserved in the pleurothotonos and opisthotonos (Fig. 10A), attitudes suggesting a condition of spastic distress, little is known about the pathology (Fig. 10B) of the animals which

FIG. 104. THE SKELETON OF Compsognathus longipes, a small Triassic dinosaur, fossilized in the position of opisthotonos, a position which has been suggested as an evidence of cerebrospinal infection. The head is thrown far back over the pelvis and tail thrown sharply up with the feet and limbs in a spastic attitude.

FIG. 10B. THE SKULL OF Mystriosuchus Plieningeri H. von Meyer, a parasuchian, from the Triassic of Aixheim, exhibiting a broken snout (above letter B) with resulting callus and bone necrosis. After Huene.

lived during the Triassic. There doubtless is much to learn in the future, since many vertebrate species are known from this period.

JURASSIC

The Jurassic of England furnishes us the first evidences of necrosis and a suggestion of metastasis as seen in the pathological nature of the bones of Metriorhynchus moreli Desl., a crocodile described by Erwin Auer from the Oxford Clay.

The skeleton of this interesting animal was only partially preserved. There are evidences of pathology in the palate, on the two femora, on a sacral vertebra and on the pelvis. Auer says:

3" Studies in Paleopathology. III., Opisthotonos and allied Phenomena among fossil Vertebrates," American Naturalist, Vol. LI., No. 617618, 1918.

4 Paleontographica, Bd. 55, pp. 277, 279-280, figs. 13-14.

On the middle of the inferior side of the palatine is a section that is unusually differentiated by cavities, and consists of fossulae, a condition that is not otherwise encountered in crocodiles, and that doubtless is connected with the pathogenic deformities the bones exhibit.

The right femur is normally formed, but it displays below the caput femoris a peculiar corrosion, and the condylus internus is reduced at the distal end.

The left femur (Fig. 11a) departs in form quite considerably from the normal type. The head of the bone has undergone a significant contraction, and the formerly globular articular surface is deformed. Under

FIG. 114. SACRAL VERTEBRA OF Metriorhynchus moreli Desl. from the Oxford Clay of England, showing carious roughening and necrosis. After Auer.

FIG. 11B. LEFT FEMUR OF THE SAME, showing pathological roughening at the upper and lower extremities, especially around the trochanetric region. After Auer.

the head of the bone the femur exhibits an abnormally small diameter, and on the external side of the bone a ridge is raised.

The sacral vertebra (Fig. 11b) also exhibits significant deformities of a pathogenic nature; the body of the vertebra is noticeably thickened, irregularly jagged on the outer side and set with numerous rather deep holes. The body of the vertebra is completely hollowed out from the end surface.

The description indicates the presence of a tuberculous or similar necrosis of the bones and is the most complete example of a seriously diseased vertebrate which has been seen in the fossil condition.

COMANCHIAN

The gigantic dinosaurs of the Comanchian have long been known to have suffered from disease and injury and the writer