SKILL OK A lUMAN FETUS 



CHARLES CMFKORD MACKI.IN 



PLATE 15 



CP. / _ 



'AM It-- ■ 



Sec 45 5^^ 59 



Sec 71 



Sec 78 



Sec 83 



Sec 99 



IS Series (if eifjlit coronal cio.ss-sectioii.s, through caudal portion of nioseth- 

 nioid, in the region of the anterior jiaraseptal cartilages. Sections numbers 35. 

 45, 59, (35, 71, 7S, S3, and 90. Magnif. 



Section 35 shows the ventral end of the ventro-lateral process, /M', and its con- 

 nection with the cauchil border of the mesethmoid. In section 45 the dorsal 

 ends of these processes are shown in cross section, with the ventral extremity of 

 the maxilla 0^17; the membranous anlage of this bone appears in sections 35 and 

 45 — .1.1/. Part of the epithelium of the nasal cavity is represented in all the 

 sections Ep. Section 59 is through the ventral end of Jacobson's cartilage and 

 shows the cranio-ventral process of the medial lamina CPi on the right side at- 

 tached to the mesethmoid, while the outer lamina, CPo lies free in the mesenchj^me. 

 Owing to the section having been cut somewhat more deeply on the right than on 

 the left side, the left side of the illustration shows a somewhat more dorsal plane 

 than does the right. The meatus of the right Jacobsonian duct opens at Jm in 

 section 59. Section 65 shows, on the right side the dorsal tip of the left outer 

 lamina of Jacobson's cartilage, and medial to this the main part of the inner 

 lamina below, and the cranio-ventral process above. The organ of Jacobson 

 ajipears in this and following sections, and it will be observed that the meseth- 

 moid has become quite thin in its vicinity, ihv. organ lying in a concavity of the 

 cartilage. In section 71 the main lamina of Jacobson's cartilage is seen CP3, 

 and it will be noted that at its caudal extremity the relationship to the maxilla 

 is very intimate. In the next section, No. 78, the caudal process is seen separated 

 from the main mass of the cartilage, and in the next section. No. S3, this process 

 has disappeared. In No. 99 the dorsal tips of the Jacobsonian cartilages are 

 seen CP;,, and below the mesethmoid, lying in a mass of condensed mcsenchj'me. 

 the anterior tips of the vomer are seen as two small spicules of bone. 



385 



