60 PROF. G. B. HOWES AND ME. H. H. SWINNERTON OJS T THE 



The Long Bones. Under this head we include the humerus and femur, radius and 

 tibia, ulna and fibula. They have all been so often described, from Giinther to 

 Osawa, that detailed recognition by us would be superfluous. We would only add that 

 the condylar foramina of the humerus, originally observed by Dollo (84), are both 

 fully formed at Stage Q (PL VI. fig. 10, f.en.^f.ec.), and that the inner lias from the 

 first period of differentiation its canal-like character. 



The long bones are the first of all the cartilage-bones to ossify. 



Carpus and Tarsus, with Phalanges. 



It is evident, from the study of both carpus and tarsus, that chondrification sets in 

 correspondingly (for the tarsus, cf. PI. VI. fig. 15). One inexplicable feature is the 

 long duration of the cartilaginous state of both. Ossification begins in both post- 

 axially (as is seen in fig. 14 for the carpus), but not until the rest of the limb is fully 

 ossified. 



We have examined both carpus and tarsus at all stages of development back to Q, 

 where these elements are first chondrified. To make sure of detail, we have employed, 

 beyond clarified dissections, serial sections cut horizontally. 



The Carpus. Giinther described ten carpal elements, and in this he has been 

 followed by others. He appears to have missed one of the centralia, and to have 

 confused the other with the proximal elements, which he describes as five in number 

 (67. p. 612). Osawa, the latest writer on the subject, correctly records eleven 

 elements (98*. p. 528), the eleventh being the secend centrale, detected by Bayer 

 (84. p. 237), who first applied to the parts a rational terminology. It was, however, 

 independently discovered by Dollo arid Baur (86 a . p. 188), the latter opposing Bayer's 

 conclusion that its supposed absence is due either to disappearance or union with 

 another carpal element. In this he was right, for we find it always present. 



None of the afore-mentioned observers describe the precise size and relationships 

 of the two centralia to each other and the adjacent carpal elements. Osawa, however, 

 gives a very different delineation to the dorsal and ventral aspects of the same pair, 

 and figures the prseaxial as outwardly extended between the radiale and first carpale as 

 seen from the dorsal surface (08 a . p. 527, figs. 13 & 14). While we can confirm the 

 accuracy of this, we are able to record further suggestive details. From a comparison 

 of our figs. 12 and 13 (PL VI.) which represent the opposite carpales of the same 

 individual, we find that the right (fig. 12) is normal but that the left (fig. 13) is 

 exceptional, in the fact that the preeaxial centrale (pr.c.) is smaller than the postaxial 

 (po.c.} and lies wholly between the radiale and the first carpale, instead of merely ex- 

 tending between them. The postaxial centrale, on the other hand, is correspondingly 

 enlarged, whereby it articulates with the second carpale, as well as with the third and 

 fourth, to which alone it is usually related. There is thus to be observed an inverse 



