Resumen por el autor, Roy Lee Moodie, Departamento de Anatomia, Universidad de Illinois.

La naturaleza del sistema Haversiano primitivo.

Los huesos mas antiguos, encontrados en el Sillirico y el Devhico, carecen de verdaderos sistemas Haversianos, que se desarrollan prinieramente con cierta extensi6n en Dinichthys, del Dev6nibo. En este pea acorazado alcanzan el mAximo de desarrollo en conexibn con el proceso dentario de la maxila y premaxila. Las lagunas participan de la naturaleza de 10s odontoblastos ; 10s canaliculos nunca comunican entre si; la laminilla fibrilar existe; las fibras perforantes no se hail desar- rollado; el canal central es ancho. El polariscopio es ~ t i l para distinguir la naturaleza de 10s sistemas Haverisanos primitivos. KO existen pruebas sobre la evoluci6n de la estxuctura del hueso; se percibe un canibio bastante brusco con la introduccih de las formas de mamiferos.

Translation by JosG F. Nonii1t.z Coriirll t-ni\-eraity >Ierliral College, K. T

ACTBOR'B ABBTRACC OF Talk3 PAPER ISSUED BY TEE BIBLIOQRAPEIC BERVICE, YAY 10

ROY L. MOODIE

Department of Anatomy, L'niversitg o j Illinois, Chicngo

ONE PLATE (THREE FIGURES)

The term Haversian system is necessarily of very general sig- nificance and is used in a broad way to distinguish any concentric arrangement of osseous lamellae around a central canal. It is often difficult to distinguish between a dentinal system, that is, a concentric arrangement of dentine, around a dmtinal tubule and a true Haversian system as seen in long bones, since the two often grade into one another. The presence of lacunae does not seem to be essential to an Haversian system, though they usually are present. In the fishes, both modern and ancient, osteoid tissue, largely lacking lacunae, may arrange itself around a vas- cular opening and thus have all the appearances of an Haversian system, and give the same orthorhombic light reactions under polarized light.

The type of such a system may be taken as those most highly specialized Haversian arrangements seen in the long bones of man, especially in the femur. From this complete system down to a slight lamellar arrangement of substances one may find all gradations in a series of fossil bones representing the history of the vertebrates from the Devonian to the Pleistocaie. Such a review has been made, and it will doubtless be of interest to de- scribe and illustrate the most ancient Hal-ersian system of which we have any knowledge.

There is no apparent indication of a gradual evolution in form of the Haversian system from the most ancient vertebrates to modern mammals, although there is a gradual development in the form of the lacunae and canaliculi. The reptiles do not

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48 ROY L. MOODIE

show a higher type of Haversian system than do the amphibians or fishes, as they do in their skeletal organization. Haversian systems in dinosaurs are as primitive as they are in Devonian fishes. They seem to have sprung into existence full formed without undergoing the process of evolution such as has obtained in the bodily organization of the vertebrates.

The most ancient organization of osseous elements which sim- ulate an Haversian system are to be found in the dental process of the premaxilla of a Devonian arthrodire, Dinichthys (figs. A and B), allied by some paleontologists with the lung fishes. This arrangement is well known to paleontologists and has been described by Claypole (94). These curious structures are not present in other portions of the a m o r of Dinichthys and are to be regarded as specialized dentinal systems, though not found in the true teeth which are not connected with the cranial skele- ton. The Haversian canal resembles a dentinal tubule, the the lacunae are those seen in the cementum of modern fishes, the lamellae are fibrillar and partake of the characteristics of dentine as seen in the teeth (fig. C) of Carboniferous sharks, the interlamellar space is filled with cement and there are true inter- stitial lamellae, though never any of the type due to the partial absorption of other Haversian systems. I have not seen this type, known as false ibterstitial lamellae in any fossil verte- brate. The orthorhombic light reaction under polarized light is exactly like that of the highly specialized Haversian systems in the femur of man. The canaliculi from the lacunae communi- cate neither with each other nor with the central canal, nor do they do so in any fossil vertebrate below the mammals. The lacunae are not confined largely to the interlamellar spaces, as they are in mammals, nor is there any apparent plan in their arrangement. Often, as in a Permian reptile, one finds three lacunae grouped together, surrounded on all sides by wide areas of osteoid tissue lacking lacunae.

The use of polarized light is essential to an adequate under- standing of the structure of fossil bone, since usually under pol- arization, lamellae, fibrillae, canaliculi, and other minute his- tological units, invisible under ordinary light, stand out with

NATURE O F PRIMITIVE HAVERSIAN SYSTEM 49

startling distinct’ness. The importance of this has been com- mented upon by various authors in their studies on the histo- logy of fossil structures.

h e y (‘19) has recently called attention to the presence of Haversian systems in the membrane bones of man. The sys- tems he described and figured, however, cannot be called true Haversian systems, but resemble those seen in fossil reptiles. It is interesting to note in the temporal bone of an Oligocene mammal an arrangement of substances exactly similar to those described by Arey for man. These ,intermediate or pseudo- Haversian systems often fail to give an orthorhombic light re- action, as they do in the case of the Oligocene mammal. The difference between the true and the intermediate types of sys- tems is to be found in the absence of intercommunications of the canaliculi with either the central canal or other lacunae and in the occasional failure to secure the same light reactions. In all other respects they are similar.

The review was undertaken with the idea of gaining a con- ception of tissue organization in ancient vertebrates so that I might judge as to the disturbing effects of pathological processes upon the structure of the part. The presence of osteoid tissue in ancient vertebrates is a normal condition. Kolliker (‘57) noted that many fish bones are composed entirely of osteoid tissue. One interesting effect in pathological conditions of fos- sil bone is to stimulate the growth of pseudo-Haversian systems, and to increase the vascularity of the bone. The same fact has been noted by Foote (‘16) in the fractured femur of a frog, where Haversian systems are ordinarily absent.

SUMMARY

Primitive Haversian systems of the very ancient vcrtebrates differ but slightly from highly developed systems of modern mammals and have been but slightly modified by the passage of time. Each group of vertebrates has its own type of lacunae, but the organization of the Haversian systems remains the same. The concentric arrangement of lamellae is not an incident of

50 ROY L. MOODIE

evolution, but a response to the mechanical laws of organiza- tion of the part. True Haversian systems are confined to the mammals .

A more complete account and niore adequate illustrations will be found in the Williston Memorial Volume now in preparation.

BIBLIOGRAPHY

AREY, L. B. On the presence of Haversian systems in nienibrane bones.

CLAYPOLE, E. W. 1894 Structure of the bone of Dinichthys. Proc. Amer.

FOOTE, J. S. 1916 Comparative histology of the femur. Smithson. Contrib.

KOLLIKER, A. On the different types in the microscopic structure of Proc. Roy. Foc. London, 1857, vol. 9,

1919 Anat. Rec., vol. 17, pp. 5942.

Micros. Soc., vol. 15, pt. 3, pp. 159-191, figs.

t o Knowledge, vol. 35, no. 3.

the skeleton of osseous fishes. 1857

pp. 656-66s.

PLATE

PLATE 1

EXPLANATION O F >l (>I ;RES

A A field in a sectionof the premasilla of Dinichthys, a Devonian -4rthrocIire, showing the distribution of the oldest known representatives of the Hnversian systems. Two syskms, a t the lower left-hand corner show the concentric lamellae.

B A single systeni showing large sizc of central canal, concentric Ianiellae, distribution of lacunae and nature of ground substance, which under polarized light, is seen to be fibrillar. The black band a t the left. lower corner is a post- fossilization crack and has no significance in t,he histology.

C Dentinal tubules of Mazodus, a carboniferous shark, for coiiiparison with the specialized systems in Dinichthys above.

Between adjacent systems are t o be seen intcrst,itial Ianiellae. X 70

X 300

X 70.

NATURE OF PRIMITIVE HAVERSIAN SYSTEM ROY L X O O D I E

PLATE 1

53