494 MAMMALIAN ANATOMY 



lachrymal behind. At the upper part of the maxillary portion are 

 several oblique lines for the attachment of the anterior ends of the 

 upper ethmoidal scrolls. A little below the middle is a prominent 

 line running from before backward ; at its middle another line begins 

 and runs obliquely downward and backward to the floor of the fossa. 

 To the horizontal line and to the lower oblique line the maxillo- 

 turbinal is attached. Under the posterior half of the horizontal line, 

 between the maxillary and the maxillo-turbinal, is the nasal canal 

 leading from the lachrymal groove of the orbit to the nasal fossa. 

 An artificial opening is often seen at the maxillo-lachrymal suture, 

 but its anterior true opening lies under the horizontal line at the 

 upper end of the oblique line. 



The surface behind the line of greatest concavity is slightly convex 

 from above downward, and is formed above of the frontal, and below, 

 from before backward, of the lachrymal and the palatine. The portion 

 contributed by the frontal turns above into the roof. It is marked 

 below by the vertical, jagged line of attachment of the cribriform plate, 

 and by six curved lines which are directed downward and forward 

 from this line and afford attachment to the partitions between the eth- 

 moidal scrolls. At its lower edge is the almost straight suture between 

 the frontal and the bones below it. These bones form approximately 

 the lower third of this portion of the outer wall of the nasal fossa ; very 

 little of the orbito-sphenoid is seen at the posterior part. The lachry- 

 mal forms slightly less than the anterior half; then follows the vertical 

 plate of the palatine, which is pierced by the spheno-palatine foramen 

 and is continued back under the orbito-sphenoid as the lateral wall of 

 the posterior naris. 



GROWTH OF THE SKULL. 



The rate of growth of the skull was obtained by observing the 

 degrees of its development in cats of the following ages : shortly before 

 birth, at birth, at three days, at seven days, at eleven days, at fifteen 

 days, at twenty-three days, at thirty days, at thirty-five days, at forty- 

 four days, at sixty days, at seventy days, at eighty days, at eighty-six 

 days, at ninety days, and at one hundred and twenty days. Seven of 

 these cats were from two litters of the same mother and were reared 

 under similar conditions. From the winter litter were obtained those 

 eleven and forty-four days old ; from the spring litter, those thirty, 

 sixty, and seventy days old ; from the summer litter, those twenty-three 



