30 



THE VEKTEBRATA OE VERTEBKATES. 



one and the same plan they are higher and lower expres- 

 sions of one and the same style of animal architecture. 



It may be added here, that in all the Yertebrata, except 

 the amphioxus, the neural canal widens in the anterior end 

 of the body, in accordance with the greater size of the 

 nervous mass which it incloses. 



Although, as just explained, a skeleton of bony material 



FIG. 29. 





Section of a portion of the surface of the shaft of the human femur, a, Haversian 

 canals; b, Lacunae. Magnified 100 diameters. 



Fro. 30. 



Part of a transverse section of the shaft of the humerus. a, Haversiau canals; 6, 

 Lacunas, with their canaliculi. Magnified 300 diameters. 



FIG. 31. 



Lacunae with the canaliculi ; from the parietal bone. The clots represent the divided 

 canaliculi, and their orifices opening into the Lacunas. Magnified 450 diameters. 



