242 RHEUMATISM. 



the character of used animal tissues, and the process of nutri- 

 tion, to arrive at a more satisfactory understanding of cause 

 and effect, remains to be seen. 



Causation. — The causes which seem to operate in the pro- 

 duction of rheumatism are generally spoken of and regarded 

 under two groups. 



1. The Indiuelling, or Prexlisiiosing, which are also often 

 hereditary. We may not as yet be able to lay the finger upon 

 the specific indwelling factor of the disease, and say of this 

 something definite and tangible that its existence in the 

 animal body, and it alone, is the predisposing cause in produc- 

 ing this diseased condition. Still reasoning from analogy, and 

 from comparing the phenomena occurring with other strange 

 appearances, the causes of which we are tolerably well aware of, 

 we are forcibly drawn to the admission that in all cases of 

 rheumatism it is highly probable that a peculiar something, 

 whether it be formation of solids, composition of fluids, or 

 peculiar modes of manifestation of nervous or other power, 

 which we have named a diathesis, or constitutional tendency 

 to develop this special manifestation of symptoms which we 

 find characteristic of rheumatism, exists in certain animals. 

 This constitutional tendency is in some so marked, and con- 

 stitutes so striking a peculiarity, that the outcome and appear- 

 ance of the disease are often, to our observation, called into 

 existence without any inducing agency whatever. While what- 

 ever adverse influences are brought to bear on animals so con- 

 stituted, which in others tend to the production of very 

 different and opposite diseases, in them, as a rule, terminate in 

 rheumatism. 



That this constitutional predisposition is hereditary, or 

 capable of transmission as an inheritance from parent to 

 progeny, can be satisfactorily established by evidence collected 

 by many and competent observers ; although this point has 

 not, in my experience, been so well established and so promi- 

 nently brought forward, as respects the horse, as it has in cattle, 

 I am still aware of facts sufticient to satisfy me of its truth. 



2. Exciting or Directly Operating. — These include all influ- 

 ences, sanitary and dietetic, which result in a lowering of the 

 vital energies, or disturbance of the process of nutrition, as 

 undue confinement, want of cleanliness, imperfect ventilation, 



