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Studies in the Medicine of Ancient India, Part I: Osteology, or the Bones of the Human Body c7.s3.t3: § 63. Cranial Bones

Studies in the Medicine of Ancient India, Part I: Osteology, or the Bones of the Human Body c7.s3.t3

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§ 63. Cranial Bones

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1. Śiras, cranium or brain-case; śiraḥ-kapāla, cranial pan-shaped bone. These two terms are employed in all the three lists, which differ only in respect of the number of the bones. While Charaka (§ 4) counts four, Suśruta (§ 27) counts six bones; and Vāgbhaṭa I (§ 37) adopts the count of Suśruta.

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² The brain-case or cranium is a hemispheroidal, oval box, made up of eight bones, namely the frontal, the two parietal, the two temporal, the occipital, the sphenoid and the ethmoid (Figs. 25, 26). Nearly the whole of it, viz. the entire vault and the larger portion of the base, is externally visible: the remainder of the latter lies internally within the skull. The externally visible portion of the cranium comprises six bones, the frontal, the two temporal, the two parietal, and the occipital. The interior, invisible portion comprises two bones, the sphenoid and the ethmoid. These two interior bones, including the small portion of the sphenoid, which shows externally by the side of the frontal (Fig. 25), were not known to the Indian anatomists. As pointed out in § 45, cl. 3, their method of dissection would not enable them to discover them; and so far as the two cranial surfaces of the sphenoid bone (Fig. 32) are concerned, they do not seem to have recognized their existence as separate from the frontal bone and as belonging to the sphenoid. In all probability

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they took them to be but continuations of the contiguous frontal bone. As to the temporal bones, they are peculiarly liable to detachment from the rest of the bony case; and it may have been for this reason that they were separately enumerated by the Indian anatomists; they are dealt with

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[Figure: FIG. 25. PROFILE OF THE SKULL. From the right. Showing—Fr. = Frontal bone Pa. = Parietal ,, } Śiraḥ-kapāla. Oc. = Occipital ,, Tm. = Temporal, Śaṅkhaka. Sp. = Sphenoid. E. = Ethmoid (in inner wall of orbit). Ma. = Malar, Gaṇḍakūṭa. N. = Nasal, Nāsikā. S. Mx. = Superior maxillary } Hanu. I. Mx. = Inferior maxillary]

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in the next paragraph. There remain only four bones, the frontal, the two parietal, and the occipital; and there can be no doubt that it is these four bones which are referred to in the list of Charaka as ‘the four pan-shaped bones of the cranium’. They are more or less decidedly concave bones, and therefore are rightly described as pan-shaped (Figs. 27, 28).

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3. The list of Suśruta substitutes six pan-shaped bones in the place of the four bones of Charaka. In order to understand this

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Ma. P P Ma. Mx Mx Sph Sph Tm. Tm. Pa. Pa. Oc.

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FIG. 26. OUTLINE OF BASE OF SKULL. Viewed from below. Showing—Oc. = Occipital. Mx. = Superior maxillary. Pa. = Parietal. Ma. = Malar. Tm. = Temporal. P. = Palate. Sph. = Sphenoid. E. = Ethmoid (not visible).

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a

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FIG. 27. FRONTAL BONE, Śiraḥ-kapāla. Internal Surface, showing frontal crest a.

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difference we must remember that Suśruta’s osteological system is strictly dominated by the principle of homology (§ 28), according to which the skeleton is considered as consisting of two lateral halves divided by a mesial plane running through the vertebral column. This plane cuts the frontal and occipital bones into two halves. As a matter of fact, these two bones consist of two halves, indicated by the frontal and occipital crests respectively (Figs. 27 and 28). In the case of the occipital bone, it is true, the two halves coalesce into one from the beginning of

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FIG. 28. THE OCCIPITAL BONE, Śiraḥ-kapāla. Internal Surface, showing occipital crest a, a.

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embryonic development; but in the case of the frontal bone they remain separated by the metopic suture, and do not become fused till about the fifth or sixth year after birth. In fact, traces of the metopic suture persist throughout life between the two superciliary ridges of the frontal bone; and in a certain percentage (about 8 per cent.) of individuals even the whole of it persists in the adult¹ (Figs. 29, 32). Either of the two halves of the frontal and occipital bones forms a separate cavity, divided by their respective crests (Figs. 27 and 28). Thus Suśruta is justified in counting ‘six pan-shaped bones of the cranium’, these being, on his principle of division, two frontal, two parietal, and two occipital. In fact in this particular, his system marks an advance on that of Ātreya-Charaka, inasmuch as it shows Suśruta’s acquaintance with the existence of the metopic suture. He had, no doubt, observed its surviving traces between the superciliary

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¹ I am indebted to Professor Arthur Thomson for the suggestion of this explanation.

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[Figure: FIG. 29. FRONTAL BONE, Siraḥ-kapāla. Anterior view, showing—a. Metopic suture. b, b. Superciliary ridges.]

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ridges, and may even have noticed the exceptional occurrence of a ‘metopic skull’. The division of the occipital bone into two halves, however, was the natural resultant of his homological principle.

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