304 



STUDY OF PIG EMBRYOS. 



in it: (i) The anlage of the vertebra, Vert, which is now quite well denned; around 

 the edge of it the cells have assumed an elongated form and have elongated nuclei; 

 the elongation is parallel with the surface of the anlage. These cells result from 

 the commencing differentiation of the perichondrium, which at this stage merges 

 on the one side into the anlage of the vertebrae, and on the other into the sur- 

 rounding mesenchyma. The cells of the vertebra have changed into young car- 

 tilage-cells. They are now distinctly separated from one another by a well-devel- 



Vert. 



D.R. Ec.gl. Sp.c. 



Nch. 



Ve'. 



Ve". 



card. 



N.io. 



bro. 



Lu. 



Piece. 



EIG? 208. PIG, 17.0 MM. TRANSVERSE SERIES 51, SECTION 464. 



Ao, Aorta, bro, Entodermal bronchus, card, Posterior cardinal vein, cin, Neurone layer (cinerea) of spinal 

 cord. Cost, Anlage of ribs. D.R, Dorsal root. Ec.gl, Ectoglia. C, Ganglion. Li, Liver. Lu, Lung. 

 muse, Dorsal musculature. N.io, Vagus nerve. Nch, Notochord. (E, (Esophagus. Pl.cce, Pleural 

 ccelom. R.D, Ramus dorsalis. R.V, Ramus ventralis. R.sy, Ramus sympathicus. Sp.c, Spinal cord. 

 Sym, Sympathetic ganglion. Ve', Ve", Branches of the subclavian vein. Vert, Vertebra. X 22 diams. 



oped matrix. Each cell occupies a separate space or capsule in the matrix. The 

 protoplasm of the cell, having changed to a transparent substance and being un- 

 stained, seems to have disappeared, but the nucleus remains distinct, for it stains 

 readily, has a sharp outline, and contains a number of dark granules, one or two 

 of which are conspicuous by their greater size and irregular shape. The nucleus 

 itself, in most of the cells, is somewhat irregular in outline, as if distorted by 



shrinkage. Toward the center of the anlage the cytomorphosis is most advanced. 



. 



