DISEASES OE THE OX AND SHEEP. 626 



cavity of the skull, the brain being absorbed as they proceed 

 inwards. Sometimes these bony growths reach a great size and 

 weigh a considerable amount. Moreover, they become moulded 

 against the walls of the skull, and present grooves marked out 

 on their surface for blood-vessels. Hence they are sometimes 

 looked upon as ossified brains ; but they are merely ingrowths 

 of bone into the cavity of the skull. The strangest fact in con- 

 nection with them is that as a rule they do not seem to interfere 

 greatly with the animal's welfare, and they may be found to be 

 present in oxen which, while living, did not appear to be very 

 unhealthy. 



Bony growths, also, as indeed we mentioned above, may occur 

 around the margin of the orbit, and so interfere with the eye. 

 They should be removed by the aid of a suitable saw, when it is 

 possible ; but when they grow from the ribs into the chest-cavity 

 it is not advisable to operate. The bony growths we have been 

 describing are called exostoses, because they arise from bone. 

 The term '* osteophyte " is applied to a spongy and vascular 

 exostosis of periosteal growth. At first it is but feebly attached 

 to the bone ; but at a later stage it may become dense and firmly 

 fixed to the bone. 



We have previously described the disorder known as fragility 

 of the bones; but in talking of bones we may mention this 

 subject again, and also that of rickets. Now, fragility of 

 the bones is the name given to a condition of them in which 

 they are liable to break easily. This state of bones results from 

 a diminution in the amount of animal constituents of the bone 

 tissue, or from an excess of the earthy material, which last in 

 either case preponderates so much as to render the bones brittle. 

 The disease is in fact due to atrophy of the bone, the animal 

 constituents being, relatively to the inorganic constituents, very 

 largely increased. The disorder is sometimes known under the 

 appellation of cripple, and it affects oxen, and especially milch- 

 cows, in certain localities. 



It may either be occasioned by a deficiency of phosphates in 

 the food, or by the fact that they are secreted in too great 

 quantity by the medium of the milk, or to some other cause of 

 debility. Further, the lack of phosphates in the food may spring 

 from a want of these salts in the soil, and this in its turn may 

 result from that grave evil, over-stocking the land, from which 



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