Rarefying Osteitis, etc. 585 



are not all due to one essential cause, manifesting itself different- 

 ly according to the activity of trophic processes in the bones of 

 the victim. In the growing foal the active developmental pro- 

 cesses in the epiphyseal ligament and periosteum may determine 

 that the sjnnpttmis shall be pre-eminently those of rickets, 3'et we 

 often see these complicated by the facial and other lesions of os- 

 teoporosis. Both may be the result of one etiological factor, or 

 there may be a complex disease resulting from the presence of 

 two. Again in the pregnant cow in which the relaxation of the 

 ischio-pubic SN^mphysis and pelvic ligaments means a pro- 

 found change in the bone nutrition at this point, the presence of 

 the hypothetic microbe, or other essential factor, ma}^ determine 

 a decalcifying and fragility of the pelvic bones generally. Again 

 in the mature male and non-breeding female, in the absence of 

 the disturbing conditions of nutrition just named, tlie vascular 

 elements in the Haversian canals and cancelli may determine the 

 simple rarefaction and expansion of the bone which characterizes 

 osteoporosis. When present in the bone in an}^ of these condi- 

 tions, acids doubtless fulfill an important role in the decalcifying 

 and softening process, but behind these it may be surmised that 

 there is an unknown cause or causes, which it is for the bacteri- 

 ologist, chemist or botanist to discover. 



Symptoms. Tliese are largely the same as in brain disease. 

 There may be first a period of illness, with poor appetite, lack of 

 spirit and energy, early perspiration and fatigue, or if at large, 

 leaving the herd, soon followed by some stiflfness of gait and lame- 

 ness, which may be intermittent, disappearing under exertion, or 

 shifting from one joint or limb to another after the manner of 

 rheumatism. Sometimes it shows in stiffness of the neck, so that 

 the patient finds difficulty in lowering the head to graze ; in 

 others the back and loins are stiff and arched .so that the animal 

 has difficulty in rising and turns slowly and painfully ; in still 

 other cases the dorsal and lumbar vertebrae are depressed so that 

 the back is hollow. Even before the manifestation of lameness, 

 the affected limb may stand forward at the fetlock or knee, the 

 gait is clums}' and awkward, and the patient may suddenly 

 stumble and fall, showing little or no power of prompt recovery of 

 balance. A horse, and especially a young horse, with this habit 

 of stumbling is always to be suspected. The long bones of the 



