306 REVIEW OF BIOLOGY 1 . 
groove, hollowed between the two plates of that bone. The 
apophysis of Ingrassias, yet cartilaginous, penetrates also in the 
’frontal and reach in contact to the external lamella, which it 
Closes with the summit of its convexity. Sometimes it perfor¬ 
ates the frontal, appears at the superficy, and the horse has a horn. 
This cartilaginous lamella is not contained entirely in the 
thickness of the orbital portion of the frontal. Its anterior half 
extends in the frontal sinus, where it forms a band entirely sur¬ 
rounded with bony tissue; this band is found in all subjects, 
even the oldest. 
When the animal gets old the extremity of the apophysis of 
Ingrassias ossifies little by little from the center to the circum¬ 
ference. In horses that have horns, aged three or four years 
old, one finds in the frontal a bony conical wedge, surmounted 
with a cartilaginous nucleus and enlarging the wing of the an¬ 
terior sphenoid. At this moment these pieces are perfectly dis¬ 
tinct from the frontal, though intimately united to it later on. 
The axis of the body of the horse belongs then to the 
primordial cranium; it is formed by the summit of the wings of 
the anterior sphenoid, which are surrounded by the frontal at the 
time of the formation of that bone. 
The similitude of position which exists between the horns of 
horses and those of ovine ruminants allows us to believe that 
there is similarity of origin between these appendages. In 
sheep, goats and like ruminants the part of the frontal where 
horns develop is exactly on a level with the summit of the wing 
of the anterior sphenoid. In bovines, the point of insertion of 
horns is higher up in relation to the sphenoid; but the elonga¬ 
tion of the frontal is a character which is not found in all the 
periods of foetal life, and towards the fourth month of gestation 
the keratogenous point is exactly in the same situation, in rela¬ 
tion to the sphenoid, as it is in ovine ruminants and in horses. 
The question might be asked, if the horns of ruminants, 
which to this day have been considered as depending from the 
frontal, have not for a starting point, as in horses, the wings of 
the anterior sphenoid.— Soc. de Biology. 
