360 ANATOMY AND PHYSIOLOGY OF THE HORSE’s FOOT. 
contact with the second phalanx. In the navicular bone of 
the hind foot, the compact osseous tissue is much thinner 
throughout its extent than in that of the fore foot. Not- 
withstanding its density, this cortical substance is pierced by 
innumerable minute canals for the passage of the capillary 
vessels distributed in its texture, and which ultimately ramify 
beneath the fibrous membrane on the lower face, or near the 
deep surface of the hyalin cartilage on the two upper faces of 
the bone. In some of my preparations these vessels are dis- 
tended with blood, which forms an excellent natural injection 
that permits their disposition to be readily traced. The 
surface and deeper strata of the compact tissue offer the 
usual histological features of bone — Haversian canals, lacunse, 
and their intercommunicating canaliculi. If we take a thin 
Eig. 10 # . — Horizontal section of the membrane (fibro-cartilage) which covers 
the under surface of the navicular bone. Magnified 600 diameters. 
vertical section of this substance, with its covering (which 
can easily be examined in the fresh state without any prepa- 
ratory grinding), from the tendon surface of the bone, 
parallel with and close to its transverse ridge, and view it in 
the microscope, these features will be readily made out. 
Near the surface, however, the canaliculi appear to become 
scarce, and non-ramifying lacunse more common than in the 
subjacent layers. Through the canals blood-vessels pass to- 
wards the surface from the cancellated nucleus. This face of 
the bone is very uneven, and shows depressions whose situation 
and extent vary in different specimens. Not unfrequently 
there is a sulcus near or in the middle of the transverse 
ridge, and here the vessels appear to be most numerous, as 
is the case in other regions when this kind of cavity is present. 
* This illustration was drawn from one of many specimens cut from the 
under surface of a fresh navicular bone. —Eds. 
