87 
column displacement of the boundaries of the above-mentioned regions 
has caused the existence of 5 lumbal, 5 sacral and 4 caudal vertebrae 
but, as can be shown with great probability, it is for the third time 
in the course of the phylogenetical development of the human ver- 
tebral column. In vertebral columns of the formula // it is the 
second time that such an arrangement has taken place. This follows 
from observations in a vertebral column, in which, in so far as at 
present the history of the human vertebral column is known to us, 
for the first time groups of 5 lumbal, 5 sacral, and 4 caudal ver- 
tebrae have appeared. These observations will be cited afterwards. 
This induced me, to divide the formulas into groups indicated by 
figures. This facilitates the general survey and gives, as will after- 
wards prove, still another advantage. 
Now we have still to look at the formulas ///a and J/T/o. 
From the formula ///a it appears, that now the 24th vertebra 
has obtained a lumbrosacral form. And the illustration shows, that 
the 12" pair of ribs is a little shorter than in the vertebral column 
[1L. This points to a beginning reduction of the mentioned pair of ribs. 
The form ///a is evidently analogous to the form //a and, like 
this, the vertebral column ///a shows that a removal in a proximal 
direction of the girdle of the extremity occasions a modification in 
the composition of the regions, and that the formation of a lumbo- 
sacral vertebra is again the first act in the progress of the trans- 
formation-process. 
The formula J//6 and the sketched specimen represent a further 
advancement of the process. The 24 vertebra has now become the 
first sacral vertebra, we can, however, easily conclude from the form 
of this vertebra that from a lumbal vertebra it has been transformed 
to a sacral vertebra. Of course there are now again 6 sacral vertebrae, 
as in the case of the sacra of //c and //d. In vertebral columns 
of the form /r/b we see distinetly, that the 12 pair of ribs has 
been reduced still more; in one of the specimens it is almost as 
little as the 13" pair of the vertebral column J/. 
If we take now a survey of the ten forms of the vertebral column 
just discussed, we may, in my opinion, assert that the view as if 
nine of these forms should only be insigniticant oscillations of the 
organisation, surrounding as variations or varieties a constant form 
— the normal vertebral column — in an irregular way, does not 
explain the stated facts in a satisfactory manner. On the contrary 
these facts confirm the view I have defended long since. 
It is so clear, that the discussed forms of the vertebral column 
are parts or links of a morphological succession or chain (morpho- 
