Franklin P. Mall | 437 
Table I shows at a glance the ossification centers which appear during 
the second month. Five embryos of the 39th day were cleared, and in 
two of them the clavicle and mandible are found, while in one it is un- 
certain whether or not the clavicle is ossified. When the question mark 
(?) is inserted in the table, for instance for specimen EH, it indicates 
that a hyaline body is seen, but that it is not as white as an ossification 
TABLE I. 
Giving the ossification centers present in embryo of the second month. The first hori- 
zontal column gives the number of the embryo, the second their crown-rump length in 
millimeters, and the third their probable age in days. *indicates that the bone given in the 
first column is ossified ; ? that ossification is uncertain ; and 0, that the specimen is injured. 
¢ 
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center should be. During the 40th day the maxilla also appears, to which 
are added the humerus and femur on the 42d day. Next come the radius 
and tibia on the 44th day and then the ulna on the 49th day. Several 
days elapse before the fibula appears,as was known to the olderanatomists. 
In less than a day later the scapula follows and on the 56th day the 
supraoccipital begins to ossify. During the 55th day the ribs make their 
appearance, and judging by their size, it is the 6th and 7th which ossify 
first. The ossification spreads rapidly in both directions and on the 
next day (56th) it is present in all of the ribs, with the exception of the 
1st and the 12th. On the 56th day we also find the beginning of ossifica- 
