136 CHAPTER^ 16. 



From this enumeration it will be seen that diseases and accidents 

 mostly proceed from preventable causes. Whenever, therefore, any dis- 

 ease or accident occurs, the causes should be promptly and diligently 

 sought out ; and no owner of horses should rest satisfied until he has 

 found it out and has taken measures to prevent it in future. 



270. On the propagation of disease hy infection and contagion. 



When a particular disease runs through a stable, it does not by any 

 means follow that it has been introduced or spread by infection or con- 

 tagion. On the contraiy, faulty stable accommodation, or bad ventila- 

 tion, or bad drainage, or neglect on the part of servants and such-like 

 causes, either collectively or sometimes even singly, are often sufficient 

 to develop wide-spread disease among all the animals subject to the same 

 cause or causes. 



When a disease breaks out suddenly in a stable and several animals 

 are attacked at once, it usually depends on their all being subjected to 

 the same noxious influence. In a word, similar causes produce similar 

 effects. The causes, whatever they may be, usually affect first those 

 animals which are weak and predisposed to disease of any sort, after- 

 wards those which are less predisposed, and ultimately may affect all in 

 the stable. The disease is then said to be, and is by many believed to 

 be, infectious or contagious. 



The earlier cases in any such attack do not in general arise either from 

 infection or contagion. It must, however, be borne in mind that the 

 vitiated atmosphere produced by the exhalations and secretions of a 

 number of diseased bodies congregated in a badly-ventilated place inten- 

 sify the original cause and lead to the further reproduction of the disease. 

 The mode of such reproduction will be explained hereafter. 



271. Prevalent ideas of infection and contagion a source of evil. 



The prevalent ideas regarding infection and contagion, though under 

 certain circumstances true, are nevex^theless the source of much mischief ; 

 because these agents are often accepted as the adequate and irresistible 

 cause of disease, and therefore no due or sufficiently diligent search is 

 made for the real and active source. 



272. Diseases seldom transmitted by infection or contagion. 



Very few cases of disease either in man or animals are under good 

 sanitary an'angements transmitted by infection or contagion. Certain 

 predisposing conditions are required to enable the poison, whatever it 

 may be, to take effect. It requires, for instance, a certain proximity of 

 the patient, a confined unchanged atmosphere, and as a general rule a 

 delicate, ailing, or othei-wise susceptible patient. If these conditions are 

 wanting, diseases seldom spread from one animal to another under ordi- 

 naiy circumstances. 



Many complaints, however, which in a clean, well-aired, and well- 

 drained and not over-crowded stable are quite unable to propagate them- 



