Scientia Sinica

NOTES ON THE OSSIFICATION AND GROWTH OF THE HUMAN ZYGOMATIC BONE*

Woo Ju-Kano (48382)

(Department of Anatomy, Dairen Medical Institute)

Studies on the ossification of different bones of man have been carried on for almost a century, but still not all questions are settled. One of the unsettled problems is the number of ossification centres of the zygomatic bone.

As early as 1864 Rambaud and Renault"! described 3 ossification centres for the zygomatic bone which appeared in the 8th week in an embryo and fused into one in the 5th month. According to Mall®!, however, the bone is ossified from one centre. In view of the fact that the zygomatic bone in adult skull is sometimes split transversely into 2 or 3 pieces, many anatomists thus believe that it is developed from 3 centres. This state is reflected in the popular textbooks on human anatomy in the United States of America. Morris’ Anatomy" states that the zygomatic bone is ossified from 3 centres and Gray's Anatomy"! cites both theories. Thus this problem remains to be solved.

As to the growth of the zygomatic bone after the appearance of the ossification centre, no detailed description is available so far as the present author knows.

This paper deals with these problems regarding the zygomatic bone.

MatertaL AND MetHop

The material of this study includes 84 human embryos and fetuses ranging in age from 5 weeks to full term. The age of embryos and fetuses was determined by the C-R or crown-rump length according to Patten'!, In measuring the older fetuses, the C-H or crown-heel dimension was also determined for the estimation of age.

The method used for clearing and staining embryos and fetuses generally followed the procedures suggested by Noback'”! with minor modifications as stated in the previous paper of the present author!”),

*First published in Chinese in the Collections of Dairen Medical Institute for the first Conference on Medical Science of the Northeastern Provinces in August, 1951, pp. 14—17.

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