Rarefying Osteitis, etc. 581 



Causes. We are still in the dark as to the essential cause of 

 rarefaction of ))one. There is a growing tendency to suspect a 

 niicrobian origin, and man}- facts are held to point in that direc- 

 tion. It seems to have been unknown in England in the early 

 part of the 19th century, and is not noticed by Blaine, Youatt, 

 Percivall nor other of the early writers. In Varnell's cases the 

 same man had two farms not far apart and equal in soil, drain- 

 age and stabling, stocked with horses bred from the same parents 

 with the same kind and amount of feed and work, yet on one 

 farm six cases of osteoporosis occurred, and on the other not a 

 single case. McNeil, in charge of street car stables, found 

 the disease destructively prevalent in the best appointed stables 

 and absent from others in the w^orst hygienic condition. In a 

 superior stable with 220 horses he had 47 cases in two years, and 

 in a fine stable with 100 horses he had 26 cases in the same length of 

 time. In the poorer stables, the horses bred in the same way 

 on all kinds of soils and with no difference in feeding nor 

 management e.scaped. It is the common experience in Europe 

 and America that a farm or district, which has been previously 

 free from the disease suddenly has an outbreak in enzootic form, 

 and this will last for a year or two, then remit only to appear 

 with its old force after an interval of .some years. Even during 

 the active prevalence of the disease on one or on several adjacent 

 farms, others in the immediate vicinity, and differing in no ap- 

 preciable way, geologically, hydrostatically, in buildings, food, 

 water, general management nor work, completely e.scape. Berus, 

 Hoskins and other city veterinarians have noticed, that it was 

 almost the rule, that a fresh hor.se put in the stall of one that had 

 suffered from o.steoporosis soon contracted the di.sease. 



W. L. Williams noticed on two different farms in Central Illi- 

 nois, on which the disease suddenly appeared, that for years after 

 the comparative subsidence of the affection there was an unusual 

 prevalence of spavins, splints, ring-bones and other diseases of 

 the bones. Meyer has noticed that ca.ses sent from Cincinnati into 

 the country, and that have got well, will succumb to the affection 

 if brought back into the city stables in which they originally con- 

 tracted it. 



All of this points very strongly to one of two things ; either 

 a pathogenic germ in the system of the affected animal ; or 



