( 709 ) 
has a simple form, this line of insertion coincides with the border 
of the myotome; where the myotome is elongated in a peak, this 
line of insertion crosses this peak. 
Figure I reproduces the external surface of the myotome extended 
in a plane. The black line indicates the transition of the inter- 
myotomal septum in the skin; where the myotome is elongated in 
a peak, it has distended the septum, because the line of transition is 
fixed upon the: skin. The peak is covered by this distended part of 
the septum, and as far as the peak is adjacent to the skin, this 
part of the corium is doubled by this triangular sheath. Whereas on 
the line of transition the passage of the intermyotomal septum into 
the corium is a direct one, this is not the case with this adjacent 
part of the septum, which is only loosely connected with the corium 
by means of some fibres of connective tissue. This makes it possible 
to dissect these triangular slips from the corium. 
In the same way as the myotomes, the triangular slips of the 
intermyotomal tissue overlap. In concordance with the direction of 
the peaks it is seen, that slips belonging to peaks directed towards 
the caudal end of the body cover each other, so, that the more 
caudal slip covers the more cranial one. If the peak is directed 
cranially the mode of overlapping is reversed, the more cranial slip 
being uppermost. Figure II reproduces the intermyotomal tissue as 
far as this formation is adjacent to the skin. 
On the mesial side the intermyotomal septum goes over in the 
connective tissue which covers the axial skeleton and beyond this 
forms a lamella between the left and right half of the dorsal mus- 
culature. Ventrally the same formation goes over in the fascia trans- 
versa covering the abdominal cavity. 
Figure III gives the line of passage of the intermyotomal septum. 
As can be seen there are two places where the muscular tissue is 
broken off, the myotome becoming thinner from outside to inside. 
The lamellae, where the muscular tissue is interrupted, cover each 
other and in this way two strong continuous septa are formed. 
The distance over which the muscular tissue is discontinuous in the 
neighbourhood of the sagittal plane amounts to four myotomes in 
the first septum and to three in the second. In agreement with this, 
the lamellae are built up resp. by four and by three sheaths of 
intermyotomal tissue. The dotted fields in figure III belong therefore 
together, forming one myotome, as can easily be verified by dissecting 
the myotome. 
Each spinal nerve springs from the cord with two roots, which 
separately leave the spinal canal through two foramina (AR and 
