T. Lewis and D. Embleton 
43 
the cross-bone represents the united bases of the 1st plialanges of the ord and 4th 
fingers, welded together and displaced inwards*. 
We now come to the hand of V, 40 (Fig. 13). In this the presence of the 
base of the 1st phalanx of the 3rd finger precludes the possibility of dis- 
placementf ; as a matter of i'act such a supposition is unnecessary, for the 
cross-bone may be said to represent the 1st phalanges of the 4th and 5th fingers. 
The first being horizontally and the latter vertically placed and much thickened. 
The U-shaped bone is the representative of the 2nd row of phalanges. It is 
noteworthy that the terminal phalanx of the 4th finger shows an indication of being- 
double, but however the deformity is explained the same difficulty will arise. The 
deformity of the hand is so gross that so small a factor is of little consequence. 
In concluding this section it is worthy of note that although the cross-bone 
formation is so closely allied to the process of bony syndactyly, and that this occurs 
in hands and feet, yet cross-bones are never observed in the lower extremities. 
Origin and Transmission of the Deformity. 
(a.) General. In entering upon a discussion of the origin and hereditary 
transmission of a human deformity, there are several considerations of importance. 
But before discussing them it is desirable to lay particular stress upon one fact, 
namely that the origin of the deformity in the first member of the family affected 
may be — but is not necessarily — a question entirely apart from that of its trans- 
mitted origin in later members of that family. Confusion of the two problems 
arises so frequently in medical communications that this emphasis is imperative. 
Comparing the standpoint of the clinician or pathologist with that of the 
vegetable teratologist, it will be seen that the former labours under distinct 
disadvantages. For the latter is aided by the prolific nature of the material with 
which he works, a vast number of progeny arising from a single parent and one 
generation following rapidly on another. Moreover the material is under control ; 
not only is he able to restrict the complicating factors by inbreeding, but from the 
hermaphroditic nature of much of the material he has the opportunity of tracing 
hereditary characters in a stock derived from a single ancestor. Those who 
investigate the smaller, more fertile and quickly breeding species of the animal 
kingdom, enjoy similar but more restricted advantages. The human teratologist on 
the other hand must work entirely with the mixed material provided by the 
irregular intermingling of a community. Rarely has the investigator of a human 
family the opportunity of examining three generations, and often but two or one ; 
his information has therefore to be drawn to a large extent from hearsay evidence, 
or from the old and oft-times misleading accounts of other members of the family. 
* Corresponding explanations apply to the other bones of this type. A rational elucidation of the 
hand shown in Fig. 17 has not been obtained. 
+ There is no reason to believe that an actual displacement ever takes place, but that the bone 
is developed in situ is certain from the nature of the articulations. 
6—2 
