86 
thickened processus lateralis is already connected with the right hand 
os coxae. Moreover the vertebral column //a shows, that the 13" pair 
of ribs is still more reduced; they are still only little pieces of bone 
which are however movably united with the processus transversi. 
In the vertebral column J/c we see, that the 25'k vertebra is on 
both sides of the body attached to the pars lateralis and has con- 
sequently become the first sacral vertebra. And as in the distal part 
of the vertebral column no important modification has taken place, 
we find now a sacrum consisting of six vertebrae. At the same time 
at the 20" vertebra on one side the rib has fused with the vertebra, 
on the other side the rib has remained extant. Consequently the 
vertebra has become a dorsolumbal vertebra. Now there are only 
4 lumbal vertebrae extant, as is likewise the case in //a. 
The next form, //d, develops, when, on both sides of the body, 
at the 20% vertebra rudimentary ribs have disappeared as independ- 
ent parts. This vertebra has now become the first lumbal vertebra ; 
there are again 5 lumbal vertebrae, and in the praesacral part the 
arrangement has taken place that characterizes the normal vertebral 
column. In the sacrum there are however still 6 vertebrae to be found. 
In vertebral columns of the form //e the praesacral part is con- 
form to that of ld. At the distal extremity of the sacrum, however, 
now peculiarities can be observed, showing that the 30" vertebra 
is loosened from the sacrum. In the specimen represented the pars 
lateralis is interrupted between the 29" and the 30" vertebra on 
the right side of the body, in other specimens this is the case on the 
other side or on both sides; in these cases the 30 vertebra is only 
connected with the sacrum by its body. In all these cases the 30 
vertebra has become a sacrocaudal vertebra. 
If now the 30 vertebra is separated from the sacrum also with 
regard to the body, then a vertebral column is formed that is indi- 
eated by the formula //f. This has a sacrum composed again of 5 
vertebrae. But now of course 5 caudal vertebrae are extant, because, 
as already in the form II, the 34 vertebra still closes the series. 
The consequence of a complete reduction of the 34" vertebra is 
a vertebral column of the normal form; the formula is indicated by 
IIT, which has been done for good reasons. 
If we compare namely the formuia /// with the formula //, 
appears, that the dorsolumbal boundary, the lumbosacral boundary, 
and the sacrocaudal boundary have all three been displaced one 
vertebra in a proximal direction, and that at the end of the vertebral 
column one vertebra has disappeared. 
It is not for the first time that in the so- -called normal vertebral 
