[ 119 ] 
VI. On the Formation of some of the Subaxial Arches in Man. By George W. 
Callender, Assistant-Surgeon to and Lecturer on Anatomy at St. Bartholomew' s 
Hospital . Communicated by J. Paget, F.JR.S. 
Received February 17, — Read March 16, 1871. 
In a previous communication on the formation of the bones of the face*, I described 
the manner in which the nasal and incisor processes of the maxillary lobes united with 
the fronto-nasal process, and the way in which the intermaxillary bones were shut off 
from the front surface of the face. I also described the ossification of the membrane 
which surrounds the anterior portion of Meckel’s cartilage on either side, and that of 
the anterior and mesial extremities of the cartilages themselves. I now propose to 
examine the formation of the arches below these structures, commencing with that com- 
monly known as the hyoid. 
To simplify the grouping of these several arches I propose to term them subaxial. 
The first of the subaxial arches is the fronto-nasal, the basis of which is formed by the 
trabeculge cranii. I take the notochord as the central line around which the develop- 
ment of the cerebro-spinal axis progresses. Now the trabeculae, at first two separate 
cartilage-rods, grow out beneath (in man in front of) the extremity of the notochord. 
After the fusion of the trabeculae their double origin is indicated by the median septum 
growing from their under surface. They inclose, by being prolonged forwards and 
downwards, the nasal passages, and they end in the intermaxillary bones. They are 
therefore subaxial in relation to the notochord, and conform generally to the plan on 
which the other subaxial arches are developed, the modifications which distinguish 
them being due to them terminal position, to the tubular shape of the long nasal 
passages which they have to form, and to the support which they give to those out- 
growths from the cerebral vesicles, the olfactory bulbs and the front portions of the 
cerebral hemispheres. 
The second subaxial arch grows from the lower and outer part of the alte of the 
sphenoid, and is the one usually described as the maxillary ; it is said not to contain 
cartilage. The third subaxial arch is the mandibular; it is strengthened by rods of 
cartilage (Meckel’s) growing from that in which the internal ear is developed. Of other 
points in the formation of this arch, and of the connexions of the fourth arch with the 
cartilage of the internal ear, I hope to give an account when I have examined the various 
steps in the formation and growth of the cartilaginous base of the skull. At present it 
was convenient to pass them by until I had dissected the structures in the cervical region. 
* Philosophical Transactions, 1869, p. 163. 
R 2 
