Rarefying Osteitis, etc. 591 



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

 rarefaction of bone. There is a growing tendency to suspect a 

 microbian origin, and many 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 frqm others in the worst 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 soil and with no difference in feeding 

 nor management escaped. 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 appreciable way, geologically, hydrostatically, in 

 buildings, food, water, general management nor work, complete- 

 ly escape. Berns, Hoskins and other city veterinarians have 

 noticed, that it was almost the rule, that a fresh horse put in the 

 stall of one that had suffered from osteoporosis soon contracted 

 the disease. 



W. I,. 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 cases 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 

 ■contracted it. 



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

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



